contribution margin

Imagine a lemonade stand where each cup sells for 3, and the lemons, sugar, and cup that go into it cost you 1. Every cup you sell leaves 2 in your hand — but that 2 is not yet profit, because you still owe the day's table rental and the sign you painted. That 2 per cup is the money each sale 'contributes' first toward covering those fixed costs, and then, once they are covered, toward profit. That leftover-after-the-cup's-own-costs is the contribution margin.

Precisely, contribution margin is sales revenue minus variable costs. It can be stated three ways: per unit (selling price minus variable cost per unit, here 3 minus 1 equals 2), in total (total sales minus total variable costs), or as a ratio (contribution margin divided by sales, here 2 over 3, about 67%). The crucial idea is what it is for: contribution margin goes first to pay off fixed costs, and only the part above fixed costs becomes operating income. So if fixed costs are 200 a day, you must sell 100 cups (100 times 2 equals 200) just to break even, and cup 101 onward earns real profit of 2 each.

This matters because contribution margin is the engine of nearly all short-run decisions — break-even, target profit, pricing a special order, dropping a product, choosing what to make when capacity is tight. It is sharply different from gross profit: gross profit subtracts cost of goods sold (which mixes in fixed factory costs), while contribution margin subtracts only variable costs, so it cleanly shows how profit moves with volume. A common slip is to treat contribution margin as profit; it is not — it is what remains to cover fixed costs and then build profit.