How do I calculate contribution margin for my platform startup?

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Quick answer. Take your revenue per transaction (usually your take rate) and subtract the variable costs of enabling that transaction — payment fees, support, and any incentives you pay out. What's left contributes toward your fixed platform costs and profit. How to calculate it. Contribution margin = revenue per transaction − variable costs of that transaction. For a platform, your revenue is usually your commission (take rate) on the transaction value. Variable costs include payment-processing fees, transaction support, fraud/insurance costs, and any incentives or discounts you fund to keep both sides active. Your platform's tech and team are fixed costs, spread across all transactions. An example. A ₹2,000 transaction happens on your marketplace and you take 15% = ₹300 revenue. Payment fees ₹40, support cost ₹30, and a ₹50 incentive you fund — ₹120 variable. Contribution margin = ₹180 per transaction, or 60% of your take (9% of transaction value). The trap: if incentives creep up to win activity, your contribution margin can vanish even as transaction volume grows. Our honest take. Platforms often “buy” activity with incentives and discounts — which quietly turns a healthy take rate into a thin (or negative) margin. Track contribution margin per transaction, including everything you pay out, or you'll scale a marketplace that never makes money.