Percentage Calculator with Reverse and Change Modes
Solve the most common percentage questions without forcing every problem into one formula. Choose percent of a value, what percent one number is of another, percentage change, increase or decrease, reverse percentage, or margin and markup conversion.
Select the percentage question
Percentage solution
Percentage formulas and interpretation
This percentage calculator provides a dedicated calculation workflow rather than a generic converter. A percentage problem is easiest to solve after identifying which value is the base, which value is the part and whether the percentage describes a level or a change.
Finding a percentage of a number
For “P percent of X,” convert P to a decimal and multiply by X. The calculator also shows the complementary amount left after subtracting the result from the base.
Finding what percent one value is of another
Divide the part by the base and multiply by 100. A zero base is undefined, so the calculator rejects it rather than returning an infinite percentage.
Percentage change
Percent change uses the old value as the denominator: (new − old) ÷ |old| × 100. The absolute old value makes the direction come from the numerator while preserving a meaningful base magnitude.
Reverse percentages
After a 20% discount, the final value is 80% of the original, so the original equals final ÷ 0.80. Adding 20% uses final ÷ 1.20. Subtracting 20 from the final is not the reverse operation.
Margin and markup
Markup compares profit with cost, while margin compares profit with selling price. The margin mode calculates both and shows the formulas so they are not confused.
Is percent change the same as percentage-point change?
No. Percent change is relative to the old value, while percentage-point change subtracts two percentage levels directly.
Can a percentage be greater than 100?
Yes. A part can exceed its comparison base, or a value can increase by more than its original amount.
Why is reverse percentage different from subtracting P percent?
The final value is based on a multiplier such as 0.80 or 1.20, so the inverse operation is division by that multiplier.