Calculate percentage increase or decrease between two values. Apply a percentage, find the original value, and see the formula, multiplier and worked steps.
Enter two values to see the percentage change, or choose another calculation above.
Values must use the same unit and basis. Results are rounded for display; calculations use unrounded values.
Find percentage change compares an original value with a new value. Apply an increase or decrease calculates a new value from a rate. Find the original value works backwards from the final amount and the known rate. Switching calculations fills the fields from a valid result.
Use non-negative amounts measured in the same unit and on the same basis. Enter decimals with a dot or comma, or fractions such as 3/4. Do not enter currency symbols or thousands separators. When applying a rate, enter zero or a positive rate and choose Increase or Decrease.
See the percentage or missing value, the signed change in amount and the multiplier. The comparison bars show the relative sizes. Choose display precision, swap the comparison values, or copy and download the result. Rounding the display does not round the underlying calculation.
For an original value above zero, percentage change = (new value − original value) ÷ original value × 100. A positive result is an increase, a negative result a decrease, and zero means no change. The multiplier is new ÷ original. A change from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%, with a multiplier of 1.25.
Increase by p%: new = original × (1 + p/100). Decrease by p%: new = original × (1 − p/100). To recover the original value, divide the new value by the same multiplier. Reverse mode is not the same as simply swapping a percentage’s sign. A 25% rise followed by a 25% fall changes 80 to 100, then to 75.
Comparing from zero requires division by zero, so no finite percentage change is shown. Applying a rate to zero returns zero. A 100% decrease produces zero, but reversing that decrease is ambiguous. Negative amounts are outside this calculator’s scope; decreases up to 100% keep amounts non-negative. Floating-point arithmetic is used, and results are rounded for display. Inputs stay in your browser; reloading clears them.
Subtract 80 from 100 to get 20. Divide by the original 80 and multiply by 100: 20 ÷ 80 × 100 = 25%. The new value is 1.25 times the original. Reversing the comparison from 100 to 80 gives a 20% decrease because the denominator is now 100.
Choose Apply an increase or decrease, enter the original amount, enter 15 as the rate and select Increase. For 200, the multiplier is 1 + 15/100 = 1.15 and the new value is 200 × 1.15 = 230. The increase in amount is 30.
Choose Find the original value and enter the final amount and the rate that was applied. If the new amount is 120 after a 20% increase, the original is 120 ÷ 1.2 = 100. Subtracting 20% from 120 gives 96, which does not undo the original increase.
A rate moving from 2% to 3% rises by 1 percentage point, but its relative increase is (3 − 2) ÷ 2 × 100 = 50%. Enter 2 and 3 to calculate this relative change. The displayed change in value is 1; because the inputs are percentages, that difference is interpreted as 1 percentage point.
Yes. An amount rising from 40 to 100 increases by 150%, with a multiplier of 2.5. Doubling is a 100% increase, not a 200% increase. A decrease beyond 100% would produce a negative amount, so this tool rejects it in Apply and Reverse modes.
The formula divides the difference by the original amount. If the original is zero, the denominator is zero, including a 0-to-0 comparison. Use the absolute difference to describe that situation. Applying a known rate to zero can still return zero because multiplication does not divide by the original amount.
It calculates a single change between comparable amounts or applies one rate once. It does not add compounding periods, predict future prices, calculate taxes or adjust for inflation. Use the same currency, unit, time basis and measurement definition for both values. The result is arithmetic, based solely on your inputs.