# Seasonal Planning in Ecommerce: Budget, Inventory and Campaigns for 2027 Source: https://wernerstrauch.com/en/blog/ecommerce-seasonal-planning Language: en Author: Werner Strauch Published: 2026-11-09 > How online stores plan for seasonality: calculate a seasonal index, order quantity, safety stock and reorder point, ad budget per month, campaign timing, cash flow and the 2027 ecommerce calendar with lead times. With a season planner. “We’ll order like last year, plus ten percent,” says purchasing. “In November we’re doubling the ad budget,” says marketing. “And what are we paying for the containers with in August?” asks finance. This is how seasonal planning works in many online stores: three departments, three plans, one shared calendar on the wall. Almost every retailer knows the result. During Black Week, ads keep running for a bestseller that sold out on Tuesday. In February, winter stock sits in the warehouse and only moves at a discount. And in autumn, cash runs short because everything has to be paid at once. This article turns the three plans into one. It starts with a number that surprises many people. * * * ## No, Q4 does not bring in half of annual revenue “Half of annual revenue comes in the fourth quarter” or “up to a third”: you find claims like these in many guides, usually without a source. We did the maths using the German Federal Statistical Office’s sales index for online and mail-order retail (Destatis table 45212, nominal, unadjusted). We left out 2024, because the restructuring of a large online retailer distorts the series from August 2024. The result: **November and December account for about 20% of annual revenue, the fourth quarter for about 29%.** November is around a quarter above an average month, February a good 10% below. | Month | 2022 | 2023 | 2025 | Average | | --- | --- | --- | --- | --- | | January | 96 | 98 | 93 | 96 | | February | 89 | 88 | 85 | 88 | | March | 102 | 102 | 100 | 101 | | April | 95 | 93 | 97 | 95 | | May | 99 | 100 | 96 | 98 | | June | 94 | 98 | 94 | 95 | | July | 94 | 97 | 101 | 98 | | August | 89 | 92 | 88 | 90 | | September | 97 | 90 | 97 | 95 | | October | 100 | 102 | 105 | 102 | | November | 126 | 128 | 122 | 125 | | December | 118 | 112 | 121 | 117 | [Als Excel herunterladen](https://wernerstrauch.com/downloads/tables/seasonal-index-online-retail-en.xlsx) Three things stand out: - **The peak is November, not December.** Black Week and Cyber Week pull Christmas purchases forward. From mid-December, parcel carriers stop accepting parcels for delivery before Christmas Eve. - **The rest of the year is flatter than many think.** Apart from November and December, no month is more than 12% above or below average. - **Your own store will differ.** Garden furniture, swimwear or school supplies have very different curves. The average is a starting point, not a plan. For Christmas 2026, the German Retail Federation (HDE) expects online sales to grow by 4.1% in nominal terms. Across all retail, November and December account for 18.5% of annual revenue according to the HDE. Why does the right number matter? If you plan with “half”, you buy too much for autumn, tie up too much cash and end up discounting in January. If you underestimate the season, your shelves are empty in November. * * * ## One index, three decisions Seasonal planning means linking purchasing, ad budget, campaigns and cash flow to **the same** expected demand curve. That curve is captured in a single number per month, the seasonal index. It determines: - **how much** stock you buy and **when** you order it - **how much** ad budget each month gets - **when** campaigns start and **how much** cash is tied up along the way This leads to one principle that holds every season: **No ad budget for products that won’t arrive in time.** The next five steps show how to get there. * * * ## Step 1: Calculate the seasonal index The seasonal index shows how far a month deviates from the average. > **Seasonal index:** seasonal index = monthly revenue ÷ average monthly revenue × 100 > > An index of 125 means the month is 25% above an average month. **Example:** A store had €1.2 million in revenue last year, so €100,000 per month on average. In November it made €125,000. The seasonal index for November is 125. Three rules make the index reliable: - **Use several years.** A single year contains chance events: a promotion, a supply shortage, a warm autumn. Two to three years are ideal. Forecasting literature recommends at least 17 monthly values for seasonal models. - **Remove growth.** If the store grows strongly during the year, December is higher for that reason alone. Divide each month by the average of its own year, not by a fixed value. - **Flag outliers.** Months with stock shortages or exceptional promotions should not go into the index unfiltered. Calculate the index not only for the whole store but for your main categories. A category with an index of 180 in May needs a different plan from one with 140 in November. * * * ## Step 2: Forecast demand for the season The simplest useful forecast is: planned annual revenue ÷ 12 × seasonal index. With a €3 million annual target and an index of 125, that is €312,500 for November. > **Simple seasonal forecast:** monthly forecast = annual target ÷ 12 × seasonal index ÷ 100 > > For products or categories, calculate in units instead of euros. For purchasing, you need the forecast in units, for your most important products. Three questions help: 1. **What is new?** New products have no index of their own. Use the index of a similar product. 2. **What is changing?** New marketplaces, higher prices, a big influencer deal or a promotion that did not exist last year. 3. **How good was the last forecast?** Measure the gap between plan and actual per month. If you don’t know your forecast error, you can’t set a sensible safety stock either. Software and AI can help with many SKUs. But they don’t replace decisions about promotions, new channels or range changes. Be careful with sweeping promises like “AI cuts forecast error by 50%”. Such figures usually lack a verifiable source. * * * ## Step 3: Plan your inventory Seasonal inventory comes down to four questions: How much do I order? How much buffer do I need? When do I reorder? And when do the goods have to be ordered at the latest? ### How much seasonal stock to order Seasonal goods have a problem: whatever is left in January only sells at a steep discount. Whatever is missing in November is lost revenue. The newsvendor model from operations research helps you weigh the two. > **Critical ratio:** critical ratio = margin per unit ÷ (margin per unit + loss per leftover unit) > > The result tells you how likely your order quantity should be to cover demand. **Example:** A jacket earns a €30 margin. Leftover units sell in January at a €10 loss each. The critical ratio is 30 ÷ (30 + 10) = 0.75. You should order enough to cover demand in 75% of cases. With a forecast of 1,000 units and a typical deviation of ±200 units, that is around 1,135 units. The rule of thumb: **The higher the margin and the lower the markdown loss, the bolder you can buy.** For goods with a thin margin and a high residual value loss, order below the forecast. ### Safety stock formula Safety stock absorbs fluctuations in demand and lead time. > **Safety stock:** safety stock = z × standard deviation of daily demand × √lead time in days > > z is the factor for the target service level: 1.28 for 90%, 1.65 for 95%, 2.33 for 99%. **Example:** Daily demand varies by 8 units (standard deviation), replenishment takes 16 days, the target is 95% availability. Safety stock = 1.65 × 8 × 4 = around 53 units. ### Reorder point formula The reorder point tells you at which stock level you need to reorder. > **Reorder point:** reorder point = average daily demand × lead time in days + safety stock > > In season, use the daily demand of the season, not the annual average. **Example:** In November you sell 40 units a day instead of 25 on annual average. Reorder point = 40 × 16 + 53 = 693 units. With the annual average you would get 453 units and reorder too late. That exact mistake causes empty shelves in peak season. ### Work back from the peak to the order date The latest order date is the start of the season minus the total lead time. - **Production:** often 30 to 45 days for goods from the Far East - **Ocean freight Asia to Northern Europe:** about 30 to 35 days via the Suez Canal, 42 to 48 days around the Cape of Good Hope. Carriers are expected to fully return to the Suez route in the first quarter of 2027, with a risk of port congestion. - **Customs, receiving, putaway:** 1 to 2 weeks, more in peak season - **Buffer:** at least 2 weeks, because only around 60% of container ships arrive on time For Black Friday 2027, this means: goods from the Far East usually have to be ordered **by early August 2027**. Spring has a second trap: Chinese New Year falls on 6 February 2027, and production there stops for two to six weeks. Goods for Easter and Mother’s Day should therefore be in production before mid-December 2026. Key metrics for steering during the season are the [sell-through rate](https://wernerstrauch.com/en/glossary/str-sell-through-rate) and [inventory turnover](https://wernerstrauch.com/en/glossary/itr-inventory-turnover). How expensive empty shelves are is covered in the glossary entry on [out of stock](https://wernerstrauch.com/en/glossary/oos-out-of-stock): according to IHL Group, retail loses around 6% of revenue worldwide through out-of-stocks and overstocks, about two thirds of it through out-of-stocks. * * * ## Step 4: Spread the ad budget across the year Many stores plan the same ad budget every month, or go by gut feeling. A simple rule works better: **the ad budget follows expected revenue.** If you plan with a fixed [marketing efficiency ratio](https://wernerstrauch.com/en/glossary/mer-marketing-efficiency-ratio), meaning revenue per euro of advertising, the budget per month follows directly from the seasonal index. Three adjustments make the plan realistic: - **Extra budget for the peak.** On Meta, the cost per thousand impressions (CPM) in Black Friday week 2025 rose by a median of 59% compared with September, measured across a sample of large, mostly US advertisers, and by 84% on Black Friday itself. At the same time, the conversion rate rose by 48% and cost per purchase fell by 20%. So more expensive reach is not automatically bad. But if you go into November with your September budget, you lose reach. Plan 20 to 40% extra budget for November and check it against your own numbers. - **Budget only for products in stock.** Before the budget goes up, check the promoted products against inventory. A bestseller that sells out during Black Week burns ad spend and customer trust. - **Adjust targets per phase.** In the warm-up phase in October, you collect reach and email addresses, which can be less efficient. In the peak, revenue counts. More in the article on [ROAS](https://wernerstrauch.com/en/blog/roas-return-on-ad-spend). * * * ## Step 5: Plan your campaigns A seasonal campaign has three phases. 1. **Warm-up (4 to 6 weeks before):** build newsletter sign-ups and audiences, test creatives, build landing pages. If you want to reach customers by email in November, you need to collect the addresses in October. 2. **Peak:** campaigns are already running. They get scaled, not launched. 3. **Follow-up:** turn peak customers into repeat buyers, sell off remaining stock, plan for returns. There are two technical pitfalls: - **Meta needs time to learn.** An ad set leaves the learning phase after about 50 optimization events within 7 days. Significant changes reset it. So launch peak campaigns 2 to 3 weeks in advance and raise budgets step by step rather than in jumps. - **Use Google Ads “seasonality adjustments” only selectively.** They tell Smart Bidding that the conversion rate will rise sharply over a short period, for example during a three-day sale. Google recommends them for periods of 1 to 7 days. From about 14 days, they work less well. You don’t need them for normal seasonality like the Christmas season, which Smart Bidding already knows. Plan discount campaigns legally, too: in the EU, anyone advertising a strike-through price must state the lowest price of the last 30 days. If you discount in October, you lose the regular price as a reference in November. More in the article on [strike-through prices and the 30-day rule](https://wernerstrauch.com/en/blog/strikethrough-prices-price-indication). * * * ## Season planner: your annual plan in one minute The season planner spreads your revenue target and ad budget across the months based on the seasonal index. It shows when the goods for each month have to be ordered and the maximum amount of cash tied up in stock. You can start with the curve of German online retail or enter your own monthly sales. Season planner Guide values, net Your annual plan Strongest month**–** Latest order date for the peak**–** Ad budget in the strongest month**–** Highest capital tied up in goods**–** Month Index Revenue Ads Order goods [Have your season plan reviewed →](https://wernerstrauch.com/en/contact) Your inputs and the result are copied into the contact form. Simplified model: goods are paid when ordered and sold in the target month, ad budget follows revenue. Destatis profile: own analysis of the German online and mail-order retail sales index (average of 2022, 2023, 2025). As of November 2026. * * * ## Cash flow: financing the seasonal dip Seasonal planning is also financial planning. With goods from the Far East, the year often looks like this: - **July and August:** order and down payment, often 30% - **September and October:** balance on shipment, freight and customs - **November:** highest ad spend - **December:** highest cash inflow - **January:** returns are refunded, remaining stock has to be sold off Between the first payment and the cash coming in from sales, three to five months can easily pass. The season planner shows the month in which the most cash is tied up in stock. That amount has to be covered by equity, a credit line or financing. More on the metric in the glossary entry on [working capital](https://wernerstrauch.com/en/glossary/working-capital). Two financing options are common for online stores: - **Inventory financing:** a financier pays the supplier, and the goods serve as collateral. - **Revenue-based financing:** repayment is a fixed percentage of revenue plus a fee. Compare the total cost with the contribution margin of the financed goods. Expensive money for low-margin goods rarely pays off. * * * ## What a Black Week order really earns Peak revenue looks good. The contribution margin often doesn’t. The following example compares a normal order with a Black Week order at a 20% discount. | Item | Normal order | Black Week, 20% off | | --- | --- | --- | | Order value | €80.00 | €64.00 | | Cost of goods (45% of regular price) | −€36.00 | −€36.00 | | Ad cost per order | −€12.00 | −€12.00 | | Shipping and fulfillment | −€6.00 | −€6.00 | | DHL peak surcharges | €0.00 | −€0.69 | | Payment fees (2%) | −€1.60 | −€1.28 | | Pro-rata return costs | −€2.00 | −€2.00 | | Contribution margin | €22.40 | €6.03 | [Als Excel herunterladen](https://wernerstrauch.com/downloads/tables/seasonal-planning-peak-margin-en.xlsx) In this example, a 20% discount cuts the contribution margin by around 73%. Ad cost per order is set equal, because higher click prices and higher conversion rates often roughly cancel out in the peak. The DHL surcharges for business customers in Germany consist of €0.19 per parcel in November and December plus €0.50 from 23 November to 6 December 2026. Both also apply to returns. There is another effect many underestimate: part of promotional revenue is **pulled forward**. In a well-known study on price promotions in brick-and-mortar consumer goods retail, about a third of the extra sales came from purchases that would have happened anyway, just later (Van Heerde, Leeflang, Wittink 2004). Whether this holds for online retail is not proven. Check it with your own numbers: how do revenue and new customers develop in the two weeks after Black Week? * * * ## Logistics and returns in the peak - **Parcel volumes:** DHL reported around 12.4 million parcels in one day on the Tuesday after Cyber Monday 2025, almost twice as many as on a normal day. - **Cut-off dates:** for delivery before Christmas Eve 2026, DHL names 21 December for domestic parcels in Germany. Communicate this date in your store, or the complaints arrive on 23 December. - **Capacity:** clarify early with your warehouse or fulfillment provider how many parcels per day are possible and when extra staff will be available. More in the article on [outsourcing fulfillment](https://wernerstrauch.com/en/blog/outsource-fulfillment). - **Return windows:** Amazon regularly extends the return window for purchases between 1 November and 25 December until the end of January. Customers increasingly expect this from other stores, too. If you follow suit, returns shift into January, and so do refunds. - **Plan for returns:** if you sell a lot of fashion, expect many returns in January. According to the German retail institute EHI, two thirds of fashion retailers have a return rate above 20%. Plan staff, cash and restocking. How to measure the rate is covered in the article on [ecommerce return rates](https://wernerstrauch.com/en/blog/ecommerce-return-rate). * * * ## Ecommerce calendar 2027 with lead times Calendars with dates are everywhere. What matters is when you need to act. The lead times below apply to goods shipped by sea from the Far East. For goods from Europe or your own warehouse, they are correspondingly shorter. Dates follow the German and DACH calendar. | Event | Date 2027 | Order Far East goods by | Campaign live from | Note | | --- | --- | --- | --- | --- | | Chinese New Year | 6 Feb | orders before mid-December 2026 | – | production stops for 2 to 6 weeks | | Valentine's Day | 14 Feb | October 2026 | late January | gift bundles | | Ramadan and Eid al-Fitr | approx. 8 Feb to 8 Mar, Eid approx. 9 Mar | October 2026 | late January | provisional, depends on moon sighting | | Easter | 28 Mar (Good Friday 26 Mar) | before mid-December 2026 | early March | spring goods collide with Chinese New Year | | Father's Day in Germany (Ascension Day) | 6 May | before Chinese New Year | mid-April | finish production before 6 Feb | | Mother's Day | 9 May | before Chinese New Year | mid-April | finish production before 6 Feb | | Prime Day | not yet announced | – | – | in 2026 it ran from 23 to 26 June, earlier than usual | | Summer sale | July | – | late June | clear remaining spring and summer stock | | Back to school | late June to mid-September by German state | April | 2 weeks before school starts | school holidays differ by state | | Singles Day | 11 Nov | early August | late October | – | | Black Week and Black Friday | 22 to 29 Nov, Black Friday 26 Nov | early August | early November | keep prices stable from 23 Oct (30-day rule) | | Cyber Monday | 29 Nov | early August | early November | – | | Christmas | 24 Dec | mid-August | mid-November | carrier cut-off expected around 20 Dec | | Exchanges and January sale | from 27 Dec | – | 27 Dec | plan for vouchers and returns | [Als Excel herunterladen](https://wernerstrauch.com/downloads/tables/ecommerce-calendar-2027-en.xlsx) * * * ## The annual roadmap: who does what, and when? | Period | Purchasing and warehouse | Marketing | Finance | | --- | --- | --- | --- | | December to January | seasonal index and forecast for the new year, order spring goods before Chinese New Year | set calendar and promotion plan | annual budget and cash flow plan | | February to April | clear winter stock, review forecast error | spring campaigns | value remaining stock | | May to July | confirm Q4 suppliers, plan quantities using the critical ratio | develop creatives and offers for Q4 | secure financing for purchasing | | August | place Far East orders for Q4 | build audiences and newsletter list | down payments | | September to October | goods receipt, switch reorder points to seasonal demand | test campaigns, landing pages, keep prices stable from 23 Oct | balance payments, check credit line | | November | check stock daily, reorder | scale, budget only for products in stock | check ad spend against contribution margin | | December | communicate cut-off dates | last-minute vouchers, then existing customers | cash inflow, reserves for returns | [Als Excel herunterladen](https://wernerstrauch.com/downloads/tables/seasonal-planning-roadmap-en.xlsx) * * * ## Checklist for your 2027 seasonal planning Checkliste 0 / 16 Punkte 0 % erfüllt Zurücksetzen Data 0/3 - Seasonal index calculated per category from at least two years - Outliers like stock shortages or special promotions flagged - Last year's forecast error per month known Inventory 0/4 - Order quantity for seasonal goods weighed against margin and markdown loss - Reorder points for the season calculated with seasonal demand - Order dates worked back from the peak, including buffer - Spring goods in production before Chinese New Year Budget and campaigns 0/5 - Ad budget per month follows the seasonal index - Extra budget for higher ad costs in November planned - Peak campaigns live 2 to 3 weeks before the peak - Prices stable for 30 days before discount campaigns - Discounts on high-margin goods or overstock, not on bestsellers Finance and logistics 0/4 - Highest capital tie-up known and financed - Contribution margin per peak order calculated, including surcharges - Warehouse or fulfillment capacity for the peak confirmed - Cut-off dates and return windows communicated in the store * * * ## FAQ How do I calculate the seasonality of my online store? Divide each month’s revenue by the average monthly revenue of the same year and multiply by 100. This gives you the seasonal index. Use two to three years and take the average to smooth out chance events. How much of online revenue comes in the Christmas season? In German online and mail-order retail, about 20% of annual revenue falls in November and December and about 29% in the fourth quarter. That is the result of an analysis of the Federal Statistical Office’s sales index for 2022, 2023 and 2025. November is stronger than December. What is the safety stock formula? Safety stock = z × standard deviation of daily demand × square root of lead time in days. The factor z depends on the target service level, for example 1.65 for 95%. What is the reorder point formula? Reorder point = average daily demand × lead time in days + safety stock. In season, use the daily demand of the season, not the annual average, or you will reorder too late. How should I spread my marketing budget across the year? Let the ad budget follow expected revenue, meaning the seasonal index. Plan extra budget for higher ad costs in November and only promote products that will be in stock in time. When do I need to order goods for Black Friday 2027? For goods shipped by sea from the Far East, usually by early August 2027. That follows from production, about 30 to 48 days of ocean freight, receiving and a buffer of at least two weeks. Black Friday 2027 falls on 26 November. Are Google Ads seasonality adjustments worth it? Only for short events of 1 to 7 days in which the conversion rate rises significantly, for example a three-day sale. Smart Bidding already accounts for normal seasonality like the Christmas season. When is Black Friday 2027? Black Friday 2027 is on Friday, 26 November 2027. Cyber Monday follows on 29 November. If you advertise strike-through prices in the EU, keep prices stable from 23 October so the regular price remains a valid reference. * * * ## Conclusion: one plan instead of three Seasonality can’t be avoided, but it can be planned. The key is a shared plan for purchasing, marketing and finance, based on a seasonal index. It determines order quantities, order dates, the ad budget per month and the cash you need in summer. Once you set this up properly, you buy more boldly where the margin allows, discount more selectively and don’t burn ad budget on sold-out products in November. The best time to plan 2027 is now, while the 2026 numbers are fresh. * * * ## Sources 1. [Destatis, table 45212: sales index for online and mail-order retail (WZ 47.91), via DBnomics](https://db.nomics.world/DESTATIS/45212BM003) 2. [HDE: Christmas forecast 2025, press release (05.11.2025, German)](https://einzelhandel.de/images/presse/weihnachten/2025/PM_Weihnachtsprognose.pdf) 3. [ms-aktuell: HDE Christmas forecast 2026 (03.11.2026, German)](https://ms-aktuell.de/?p=174588) 4. [bevh: stable Christmas season expected (2025, German)](https://bevh.org/detail/stabiles-weihnachtsgeschaeft-erwartet-moebel-drogerie-und-grossgeraete-staerken-onlinehandel) 5. [Lebesgue: Meta ad costs around Black Friday 2025](https://lebesgue.io/?p=15192) 6. [Supermetrics: Black Friday Retail Playbook](https://supermetrics.com/ebook/black-friday-retail-playbook) 7. [Karooya: summary of the Tinuiti Digital Ads Benchmark Q4 2025](https://www.karooya.com/blog/digital-ads-benchmark-report-by-tinuiti-q4-2025) 8. [Google Ads Help: seasonality adjustments](https://support.google.com/google-ads/answer/10369906?hl=en) 9. [Google Ads Help: preparing for seasonal events](https://support.google.com/google-ads/answer/15302774?hl=en) 10. [Prediko: Seasonal demand forecasting (11/2026)](https://www.prediko.io/forecasting-demand-planning/seasonal-demand-forecasting) 11. [IHL Group: Inventory Distortion](https://www.ihlservices.com/product/inventory-distortion/) 12. [Seatrade Maritime: full Suez return for container carriers expected by Q1 2027](https://www.seatrade-maritime.com/containers/full-suez-return-for-container-carriers-expected-by-q1-2027) 13. [DHL business customers: surcharges (German)](https://www.dhl.de/de/geschaeftskunden/paket/leistungen-und-services/zuschlaege.html) 14. [eurotransport: DHL Black Week 2025 with record volumes (German)](https://www.eurotransport.de/logistik/spedition-und-logistik/dhl-black-week-2025-rekordmengen-ecommerce-deutschland/) 15. [Händlerbund: Amazon extends Christmas return window (German)](https://ohn.haendlerbund.de/amazon/marktplatz/rechtstexte-amazon-verlaengerte-rueckgabefrist-weihnachten-bekannt) 16. [Amazon: Prime Day 2026](https://www.aboutamazon.eu/news/retail/amazon-prime-day-2026-date) 17. [Van Heerde, Leeflang, Wittink (2004): Decomposing the Sales Promotion Bump, Marketing Science 23(3)](https://ideas.repec.org/a/inm/ormksc/v23y2004i3p317-334.html) 18. [Wego: Ramadan 2027](https://blog.wego.com/ramadan-2027/)