How to use the price increase break-even calculator
The fear that stops most price increases is losing customers. The useful question is not whether volume falls but how far it can fall before you are worse off. Because variable cost per unit does not move when the price does, every unit contributes more afterwards, so fewer units are needed to earn the same money.
Contribution margin carries the whole calculation. Margin per unit = price − variable cost per unit, and multiplying by volume gives total contribution. Keep total contribution unchanged and operating profit is unchanged too, because rent, salaries and other fixed costs sit identically on both sides and cancel. That leaves units needed = total contribution before ÷ margin per unit after, with no fixed cost input required.
Both a unit count and a revenue figure are shown, because they do not move together. The number of units always falls, while revenue can rise or fall depending on how large the increase is, so the difference against current revenue is printed on its own line. The final row is the volume drop you can absorb: as long as sales stay within that percentage, the increase leaves you no worse off. Units are whole, so the requirement is rounded up and the label says so only when rounding occurred.
Frequently asked questions
Variable cost per unit stays where it was while the price rises, so each unit contributes more. Fewer units are then needed to reach the same total contribution, and that shrinkage is exactly the volume drop you can absorb.
Units are sold whole, so a fractional result has to move to the next unit. The label says rounded up only when the division did not come out even, never when it did.
Rent, salaries and other fixed costs are the same before and after the increase, so they cancel on both sides. Holding total contribution constant therefore holds operating profit constant, with no fixed cost input required.