Unit economics describe the revenue and costs of one meaningful unit of a business, such as an order, a subscription month, or a customer. They help answer whether an additional unit contributes enough to cover fixed costs and, eventually, support a sustainable business. The choice of unit and the costs included must be stated explicitly.
Which unit should you measure?
Start with the transaction or relationship that drives the decision you need to make. A shop might use an order, a service business might use a completed project, and a subscription product might examine a customer over a defined period. Do not switch casually between an order and a customer: a customer can place several orders, while one order can include several products. If those boundaries move, the comparison becomes misleading.
Use the same time period and cost treatment for each comparison. Separate new and repeat customers or distinct product lines when their economics differ materially. A single blended average can conceal a segment where every additional sale consumes cash.
How do you calculate contribution per unit?
For a straightforward sale, subtract the variable costs associated with that sale from its net revenue. Variable costs may include fulfillment, packaging, payment processing, returns, and commissions when they are attributable to the unit. The remainder is contribution margin per unit, available to cover fixed costs. Stripe's guidance distinguishes costs that rise with each sale from fixed expenses and shows why missing transaction-level costs distorts the margin.
Acquisition spending needs a consistent treatment. You can show contribution before acquisition and subtract acquisition cost separately, or include attributable acquisition cost in a clearly labeled net figure. Do not subtract it twice. A customer lifetime estimate is a different model: it needs repeat behavior, retention, and margin over a defined horizon rather than simply multiplying revenue by an assumed number of months.
What can unit economics tell you—and what can they not?
A positive contribution per order does not mean the entire business is profitable: rent, core salaries, and other fixed costs still need coverage. A negative contribution on an incremental sale deserves investigation before buying more traffic or discounting more deeply. Compare contribution by channel, product, and customer cohort, then test why the numbers differ. Use a decision log for major pricing or channel changes, including the cost assumptions and a review date.
Treat the calculation as a decision aid, not a universal benchmark. Payment fees, returns, and fulfillment change with product mix and geography, and a service business may need to account for delivery time. Update the model from real operating records when they become available.
A fictional order-level calculation
Suppose an online business earns ₹1,000 in net revenue from an order. Product and packaging cost ₹420, shipping costs ₹90, and transaction fees cost ₹30. Contribution before acquisition is ₹460: ₹1,000 minus ₹420 minus ₹90 minus ₹30. If attributable acquisition spend averages ₹250 for a new order, the first-order contribution after acquisition is ₹210. That ₹210 still has to help cover fixed costs, and repeat orders may have different acquisition costs. The numbers are illustrative, not a margin target or a forecast. The business should check actual returns and support costs before deciding to scale that channel.