Enter your selling price, variable costs, and the marketplace fee. Get your contribution margin ratio and the exact margin each unit contributes toward fixed costs and profit.
Start with a marketplace preset (fee % is editable):
Contribution Margin Ratio
Contribution margin per unit
A contribution margin calculator shows how much of each sale is left over after you cover the variable costs tied to that sale, so you can see what each unit contributes toward your fixed costs and profit. Unlike a plain profit margin tool, this one treats the marketplace fee as a variable cost, because platforms like Shopee, Lazada, Amazon, and TikTok Shop take a percentage of every order. Enter your selling price, product cost, shipping and packaging, and the fee percentage, and you get your contribution margin per unit and your contribution margin ratio instantly.
The formula is: Contribution Margin = Selling Price - Total Variable Costs, and the Contribution Margin Ratio = Contribution Margin / Selling Price. Say you sell an item for $25, the product costs $10, shipping and packaging is $2, and the marketplace fee is 10% (which is $2.50 on a $25 sale). Your total variable cost is $10 + $2 + $2.50 = $14.50. Contribution margin is $25 - $14.50 = $10.50 per unit, and the ratio is $10.50 / $25 = 42%. That means 42 cents of every dollar in sales is available to cover fixed costs and then become profit.
Gross margin subtracts only the cost of goods sold from revenue. Contribution margin goes further and subtracts every variable cost, including shipping, packaging, payment processing, and marketplace commission, so it reflects what a sale actually leaves behind. That makes contribution margin the number to use for pricing, promotions, and deciding whether a product is worth keeping. If you only want the cost-of-goods view, use our profit margin calculator; to work out the cost side first, the COGS calculator helps.
Contribution margin per unit is what pays for your fixed costs, the rent, software, salaries, and advertising that do not change with each order. Once your total contribution covers those fixed costs, everything above it is profit. That is why the number drives your break-even point: Break-Even Units = Fixed Costs / Contribution Margin per Unit. In the example above, every $1,000 of fixed costs needs about 96 units sold to cover it. To turn that into a full break-even picture with your own fixed costs, use our break-even calculator.
Not every product deserves shelf space. A SKU with a high selling price can still have a thin contribution margin once fees and shipping come off, while a cheaper item might contribute more per unit. Rank your products by contribution margin, not by revenue, and you quickly see which lines fund the business and which quietly drain it. A negative contribution margin is a red flag: you lose money on every unit sold, and volume only makes it worse. This calculator warns you when your variable costs exceed your price.
The same product has a different contribution margin on every channel, because each marketplace charges a different fee. A 42% ratio on your own store can drop to the low 30s on a platform with a 15% commission. Tracking that by hand across dozens of SKUs and several channels is where margins leak unnoticed. OneCart syncs your inventory, orders, and pricing across Shopee, Lazada, Amazon, TikTok Shop, Shopify and more from one dashboard, and reports profit by SKU per channel, so the contribution margins you calculate here hold up in the real business.
OneCart syncs pricing, inventory, and orders across Shopee, Lazada, Amazon, TikTok Shop, Shopify and more, and reports profit per product.
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