What is contribution margin?
Contribution margin is what one order leaves behind after every cost that varies with that order, such as product cost, shipping, packaging and payment fees.
Formula
Contribution margin = order value − variable costs; margin percent = contribution ÷ order value × 100
Worked example, not a result
Taking one order apart
Say an order comes in at 64. The product inside it cost 22 to buy or make. Shipping it costs the store 6.80 after the buyer's contribution. The payment processor takes 1.90. Picking, packing and the box come to 3.50.
Those variable costs add up to 34.20, so the order leaves 29.80 behind. As a percentage that is about 46.6 percent contribution margin.
That 29.80 is the real budget for everything else. Advertising, software, staff, rent and profit all come out of it. If the store is paying more than 29.80 in marketing to win the order, the order loses money no matter what the ad platform reports about revenue.
One more subtraction is easy to forget. If a share of orders comes back, the returns handling and the lost shipping have to be spread across the orders that stick, which pulls the true contribution below the clean figure above.
These numbers are an example, not a price list.
Why it matters
Contribution margin is the number that turns every other metric into a decision. Without it, revenue based measures like return on ad spend are just ratios floating free of the business, and two stores with identical ad reports can be in opposite financial positions.
It connects all four levers to money. It sets the break even point for the visitors lever, so you know what a click can cost. It shows why average order value is worth working on, because extra basket value usually carries higher margin than the first item. It decides how much of a repeat customer's spend you actually keep. And it puts a value on conversion work, because a better converting page adds contribution without adding cost.
For a store owner the practical version is simple. Work out the contribution on your top selling products before you set a single budget, and the rest of the plan stops being guesswork.
Common mistakes
- Using gross margin from the accounting software as if it were contribution. Gross margin usually stops at product cost and leaves out shipping, fees, packaging and returns, which is where a lot of the money goes.
- Applying one blended margin to a catalogue that varies. Heavy items, bulky items and discounted lines each behave differently, and the average can hide products that lose money on every sale.
- Forgetting the cost of returns. On categories where fit or taste drives returns, the difference between the clean figure and the real one is large enough to change every budget decision.
- Ignoring discount codes and free shipping thresholds. Both are variable costs of the order, and leaving them out flatters the margin you plan against.
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