Calculating wholesale margins helps UK marketplace sellers understand true profitability after supplier costs, platform fees, shipping and returns. The basic formula is (selling price minus total costs) divided by selling price, expressed as a percentage, but accurate results require including every variable that applies to your specific channels.
This guide provides straightforward steps, ready-to-use spreadsheet structures and worked examples tailored to Amazon, eBay, Etsy, TikTok Shop, OnBuy and multichannel selling. Follow the process to set prices that cover costs and leave room for growth.
Why accurate margin calculation matters for UK sellers
Marketplace platforms charge fees that vary by category, fulfilment method and sales volume. Supplier prices, shipping, packaging, returns and occasional advertising costs all reduce the amount left after a sale. Without a clear view of these combined costs, sellers risk pricing too low and operating at a loss or pricing too high and losing sales to competitors.
Regular margin reviews let you adjust supplier choices, negotiate better rates or change product focus. They also support decisions about which platforms suit your range best. Treat margin calculation as a monthly routine rather than a one-off task.
Core margin formulas every seller should use
Use these three formulas as your foundation. Keep them in a spreadsheet so you can update numbers quickly.
- Gross margin = (Selling price − Cost of goods sold) ÷ Selling price × 100
- Net margin = (Selling price − Total landed cost) ÷ Selling price × 100
- Break-even price = Total landed cost ÷ (1 − desired margin percentage)
Cost of goods sold usually includes the supplier unit price plus import duty and shipping to your storage location. Total landed cost adds platform fees, fulfilment, packaging, returns provision and any per-order costs. Always work in pounds sterling and round to two decimal places for accuracy.
Building a practical margin spreadsheet
Create a simple spreadsheet with these columns: Product SKU, Supplier cost per unit, Shipping to you, Duty and VAT paid on import, Total landed cost to storage, Platform (Amazon, eBay etc.), Selling price, Platform fee estimate, Fulfilment cost, Packaging and postage, Returns provision, Total costs, Gross margin %, Net margin %, Notes.
Use formulas rather than manual calculations. In the total landed cost column enter =SUM of the supplier, shipping and duty cells. For net margin use =(Selling price − Total costs) / Selling price. Format percentage cells to show one decimal place. Add a separate summary sheet that pulls averages by platform or by product category using simple SUM and COUNT functions.
Keep one tab for current pricing and another for “what-if” scenarios so you can test the effect of a supplier price increase or a change in fulfilment method without overwriting live data.
Accounting for platform fees and fulfilment costs
Each marketplace has its own fee structure, which can include a percentage of the sale, a fixed per-item fee and separate charges for fulfilment when using their logistics. Check the platform’s current terms regularly because these change. Add a small buffer of 1–2 % in your spreadsheet if you expect occasional promotional discounts or advertising.
For fulfilment, compare using the platform’s service against shipping yourself. Include the full cost of picking, packing materials, courier fees and the time involved. When selling across multiple platforms, create a lookup table in your spreadsheet that automatically applies the correct fee rate based on the channel selected for each row.
Factor in return rates. Conversion rates and return provisions vary widely; benchmark against your own data depending on product type.
Worked examples for UK marketplace sellers
Example 1 – Amazon FBA fashion accessory. Supplier cost £4.80 including delivery to your supplier’s warehouse. Import duty and transport to Amazon’s fulfilment centre bring the landed cost to £6.25. Current selling price £14.99. Platform and fulfilment fees total £4.10. Returns provision £1.20. Total costs £11.55. Net margin = (£14.99 − £11.55) ÷ £14.99 = 23.0 %. This leaves limited room if advertising is added, so either source a cheaper supplier or test a higher price point.
Example 2 – Handmade jewellery on Etsy and eBay. Supplier cost per unit £2.90. No import duty. Packaging and postage £1.65. Platform fees vary; at a £12.50 selling price the total cost per sale is £5.42. Net margin = (£12.50 − £5.42) ÷ £12.50 = 56.6 %. The higher margin reflects lower fulfilment overheads but depends on the seller managing their own shipping reliably.
Use these examples as templates. Replace the numbers with your own supplier quotes and current platform fee estimates to see immediate results.
Refining your calculations over time
After three months of sales, replace estimated fees and return rates with your actual averages taken from seller reports. Add columns for monthly sales volume so you can calculate contribution to fixed costs such as storage or software subscriptions. Revisit supplier terms annually; even a 5 % reduction in unit cost can improve net margin by several points.
Consider seasonal variations. Products with higher return rates in winter may need wider margins. Test small price changes on a few listings while monitoring margin impact in your spreadsheet before rolling out across the range.
Common pitfalls and how to avoid them
Many sellers forget to include the cost of returns, packaging or the platform’s fixed per-order fee. Others rely on supplier list prices without adding transport and duty. Always calculate using the price you actually pay, including any minimum order quantity penalties spread across expected sales.
Avoid setting prices solely by adding a fixed percentage markup. Work backwards from a target net margin that leaves enough to cover your time and business overheads. Update the spreadsheet whenever a supplier changes terms or a platform updates its fee schedule.
Frequently asked questions
What is the simplest formula for wholesale margin?
Subtract all costs (supplier price, shipping, platform fees, fulfilment, packaging and returns provision) from the selling price, divide the result by the selling price and multiply by 100 to give a percentage. This net margin figure shows what remains after every direct cost.
How do I include Amazon FBA fees in my margin calculation?
Add the referral fee percentage, the per-unit fulfilment fee and any long-term storage costs. Use the latest rate card from Amazon Seller Central and enter these as separate lines in your spreadsheet so you can see the impact of each component.
Should I calculate margins before or after VAT?
Calculate using prices excluding VAT. Most UK marketplace reports show VAT separately and you reclaim input VAT on purchases. Checking current HMRC guidance ensures you apply the right treatment for your business structure.
How often should I update my margin spreadsheet?
Review it monthly using actual sales data from your platforms. Update supplier costs whenever they change and adjust return rates as soon as you have three months of reliable figures. This keeps pricing decisions based on current reality.
Can the same product have different margins on different platforms?
Yes. Platform fees, fulfilment options and typical selling prices vary. A product may be profitable on Etsy but marginal on Amazon if fulfilment costs differ. Track each channel separately in your spreadsheet to decide where to focus effort.
Related reading: Multichannel analytics dashboards for UK e-commerce, Getting approval for restricted Amazon categories UK, eBay Authenticity Guarantee for UK luxury sellers. Browse all marketplaces guides or apply to Loomworks.