A break-even calculator finds the sales volume where a business stops losing money and starts making it. Enter your fixed costs, the price you charge per unit and the variable cost of each unit, and it returns the number of units and the revenue needed to break even.
The engine behind it is the contribution margin — price minus variable cost. Divide fixed costs by that margin and you get the units required to cover everything. Sell one more and the full margin flows to profit, which is why understanding break-even is the first step in any pricing or launch decision.