Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Contribution margin per unit
$9.78
Contribution margin %
28.8%
Total monthly contribution
$2,445
Allocated returns cost per unit
$2.72
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How to use this
- 1Enter sale price ($).
- 2Enter cost of goods ($).
- 3Enter payment/marketplace fees per unit ($).
- 4Enter average shipping cost ($).
- 5Enter returns rate (%).
- 6Enter units sold per month.
- 7Read your contribution margin per unit on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
Revenue per SKU tells you what sells; contribution margin tells you what's worth selling. A bestseller with thin margin after fees, shipping, and returns can drag down profitability more than a slower SKU with fat margin. This calculator takes a single SKU's sale price and subtracts COGS, payment/marketplace fees, average shipping cost, and an allocated returns cost, giving you contribution margin dollars and percentage per unit, then multiplies by monthly unit volume to show total monthly contribution. Run this across your catalog (one SKU at a time) to rank products by total dollar contribution rather than revenue or unit volume alone, since a SKU selling 500 units a month at $2 margin ($1,000 total) may matter less to your bottom line than one selling 80 units at $18 margin ($1,440 total), despite looking far less impressive on a bestseller report.
Worked example
Using the values the calculator loads with:
Inputs
- Sale price: 34 $
- Cost of goods: 11 $
- Payment/marketplace fees per unit: 4.5 $
- Average shipping cost: 6 $
- Returns rate: 8 %
- Units sold per month: 250
Results
- Contribution margin per unit: $9.78
- Contribution margin %: 28.8%
- Total monthly contribution: $2,445
- Allocated returns cost per unit: $2.72
What each field means
Inputs
- Sale price ($)
- The sale price used in the calculation, measured in $. Starts at 34 $ so you have a working example on load.
- Cost of goods ($)
- The cost of goods used in the calculation, measured in $. Starts at 11 $ so you have a working example on load.
- Payment/marketplace fees per unit ($)
- The payment/marketplace fees per unit used in the calculation, measured in $. Starts at 4.5 $ so you have a working example on load.
- Average shipping cost ($)
- The average shipping cost used in the calculation, measured in $. Starts at 6 $ so you have a working example on load.
- Returns rate (%)
- The returns rate used in the calculation, measured in %. Starts at 8 % so you have a working example on load. Accepted range: 0–100 %.
- Units sold per month
- The units sold per month used in the calculation. Starts at 250 so you have a working example on load.
Results
- Contribution margin per unit
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Contribution margin %
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total monthly contribution
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Allocated returns cost per unit
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How is this different from gross margin?
Gross margin usually only subtracts COGS. Contribution margin subtracts every variable cost tied to selling and fulfilling that unit — fees, shipping, and returns — leaving the actual dollars available to cover fixed costs and ad spend.
Should I include fixed overhead like warehouse rent?
No, that's the point of contribution margin versus net margin. Fixed costs don't vary with units sold, so keep them out of this per-SKU number and instead check whether total contribution across all SKUs covers your fixed costs in a separate breakeven calculation.
How should I use this to prioritize inventory?
Rank SKUs by total monthly contribution, not by margin percentage or unit volume alone. A high-margin SKU with low volume might contribute less total profit than a modest-margin SKU that sells in bulk, and that total dollar number is what should drive reorder priority.
What if a SKU has negative contribution margin?
That SKU is losing money on every sale before fixed costs even enter the picture. Either raise the price, renegotiate COGS or shipping, or discontinue it, since no amount of volume fixes a negative per-unit contribution.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Contribution Margin Per SKU Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/contribution-margin-sku
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/contribution-margin-sku" target="_blank" rel="noopener">Contribution Margin Per SKU Calculator — RevenueLab</a> (2026).</p>
Source: [Contribution Margin Per SKU Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/contribution-margin-sku) (2026).