E-commerce unit economics measures what one order or one customer contributes after the costs that move with that unit. A practical model starts with net order revenue, subtracts variable order costs, then adds acquisition and repeat purchasing as separate layers.
The purpose is not to create one universal margin. It is to make each cost boundary explicit so marketing, merchandising and finance can reconcile the same order.
The order-level framework
Order contribution before acquisition = net order revenue - variable order costs
Variable order costs may include:
- product cost;
- packaging;
- payment processing;
- marketplace or platform transaction fees;
- pick, pack and fulfillment fees;
- shipping paid by the store;
- expected returns, refunds or warranty cost;
- variable customer-service or service-delivery cost.
Costs should be included because they change with the order or customer, not merely because they are easy to export from a platform.
Worked first-order example
Suppose an acquired customer’s first order has the following economics:
| Line | Per order |
|---|---|
| Gross order value | $120.00 |
| Discounts and expected refunds | -$10.00 |
| Net order revenue | $110.00 |
| Product cost | -$38.00 |
| Fulfillment and store-funded shipping | -$9.00 |
| Packaging | -$3.00 |
| Payment and platform fees | -$3.50 |
| Returns reserve | -$5.50 |
| Contribution before acquisition | $51.00 |
| Blended CAC | -$35.00 |
| First-order contribution after CAC | $16.00 |
The calculation is:
$110 - $38 - $9 - $3 - $3.50 - $5.50 = $51 contribution before acquisition
$51 - $35 CAC = $16 first-order contribution after acquisition
This order repays CAC immediately under the entered assumptions. It does not yet allocate fixed payroll, rent, software or taxes.
Use the E-commerce Profit Calculator to reconcile these unit assumptions with store-level totals. If unit contribution looks strong but period profit is weak, volume, fixed costs or an omitted cost layer may explain the difference.
Revenue definitions must reconcile
Gross merchandise value, gross sales, net sales and recognized revenue can differ. Select one starting point and show every adjustment between the commerce platform and the unit model.
For example, deducting refunds from net revenue and also including the full refunded product value in a returns reserve can double count the same loss. A reserve should represent the expected cost not already reflected in the revenue and cost lines.
Taxes collected on behalf of a government and shipping charged to the customer also require consistent treatment. The model should show whether customer-paid shipping is included in revenue and whether store-paid shipping is included as a variable cost.
Add acquisition as a separate layer
CAC belongs below contribution before acquisition because this makes two questions visible:
- Does the order create contribution before customer acquisition?
- Does that contribution recover the cost of acquiring the customer?
A paid-media CAC may help diagnose a campaign. A fully loaded CAC may be more appropriate for company planning. Use the CAC Calculator and label which cost pool is included.
Do not subtract CAC from every repeat order. CAC is incurred to acquire the customer. Repeat orders should instead contribute toward recovering any CAC not repaid on the first order and then toward customer-level contribution.
Build a customer-level view
A simple customer contribution model is:
Customer contribution before acquisition = sum of order contribution across the observation period
Customer contribution after acquisition = customer contribution before acquisition - CAC
Suppose the example customer places two additional orders with $45 contribution each. Customer contribution before acquisition becomes $51 + $45 + $45 = $141. After the original $35 CAC, contribution is $106 before fixed costs.
This historical observation is not automatically lifetime value. A lifetime estimate requires assumptions about retention, order frequency, margin and the forecast horizon. Use the Customer Lifetime Value Calculator only after defining those assumptions.
Scenario matrix
| Scenario | Net revenue | Variable cost before CAC | Contribution before CAC | CAC | First-order contribution |
|---|---|---|---|---|---|
| Base | $110 | $59 | $51 | $35 | $16 |
| 10% discount without cost change | $99 | $59 | $40 | $35 | $5 |
| Higher fulfillment | $110 | $65 | $45 | $35 | $10 |
| Higher CAC | $110 | $59 | $51 | $55 | -$4 |
| Better product cost | $110 | $54 | $56 | $35 | $21 |
The matrix shows why AOV or conversion improvements are not sufficient on their own. A discount can increase order volume while reducing contribution per acquired order.
Use the model to choose an action
| Weak point | First diagnostic |
|---|---|
| Low net revenue per order | Discount, refund, bundle and product-mix analysis |
| Low contribution before CAC | Product cost, fulfillment, shipping subsidy and fee review |
| Positive order contribution but negative after CAC | Acquisition scope, conversion rate and channel mix |
| Attractive LTV but slow cash recovery | CAC payback by cohort |
| Strong unit economics but weak store profit | Fixed costs, volume and reconciliation to period totals |
Common mistakes
- Starting from gross sales while omitting refunds and discounts.
- Treating all operating costs as variable or all payroll as fixed without examining behavior.
- Subtracting the same return cost twice.
- Applying blended CAC to returning-customer orders.
- Calling a forecast LTV an observed result.
- Improving one metric while ignoring the full contribution chain.
Unit economics is most useful as a reconciled model with versioned definitions. When fees, fulfillment contracts, product mix or return behavior change, update the affected assumptions and restate comparisons where necessary.
Start with an order
Begin with net revenue after discounts and refunds. Subtract product cost, packaging, payment fees, fulfillment and variable shipping subsidies. The remainder is order contribution before acquisition cost.
Add acquisition
Subtract paid-media or blended customer acquisition cost, depending on the decision. First-order contribution shows whether an acquired customer pays back immediately.
Add repeat purchasing carefully
Lifetime value depends on retention, order frequency, order value and margin. Use cohorts rather than a single company average when possible, and distinguish revenue LTV from contribution-based LTV.
Monitor the full chain
AOV, conversion rate, CAC and LTV can each improve while cash flow deteriorates. Maintain a reconciled view that connects platform metrics to store orders and financial results.
Sources
- Shopify: customer acquisition cost; Shopify; accessed Jul 13, 2026
- Shopify: gross, operating and net profit margins; Shopify; accessed Jul 13, 2026
- OpenStax: contribution margin and variable costs; OpenStax; accessed Jul 13, 2026
This guide is educational and does not provide financial, accounting, tax or legal advice.