Percentage Calculator (percent of, percent change, reverse percentage)
Work out X% of Y, what percent X is of Y, the percentage change from A to B, a value after a ±X% change and the original value before it — exact decimals, with clear errors for division by zero.
- Runs in your browser (no upload)
Result
100 increased by 20% is 120.
Formula: 100 × (1 + 20 ÷ 100) = 120
How to use
- Choose the calculation: X% of Y, X as a percent of Y, percentage change, increase/decrease, or the original value.
- Enter the two numbers. For increases and decreases, also choose the direction.
- The answer, the formula and the difference appear instantly and can be copied.
FAQ
What is the percentage change from 0?
Percentage change is the difference divided by the starting value, so a starting value of 0 would mean dividing by zero. The calculator shows an error instead of a misleading number; compare the difference instead.
Does a 20% increase followed by a 20% decrease cancel out?
No. 100 increased by 20% is 120, and 120 decreased by 20% is 96. To undo a change, use "Find the original value before a change" (120 ÷ 1.2 = 100).
Are the results exact?
The numbers you enter are calculated as decimals, not binary floating point. Only results that do not terminate are rounded, to the number of decimal places you choose.
Notes & limitations
- What you enter is processed only on this page and is not sent to YUCTS servers.
- Results that do not terminate (such as 1 ÷ 3) are calculated to 30 decimal places and rounded for display.
- When the starting value is negative, the percentage change divides the difference by its absolute value; some fields define it differently.
- Percentage points (the difference between two percentages) are not calculated.
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