ToolPilot
Percentage calculator
Find a percentage of a number, express one value as a percent of another, measure percent change, or add or subtract a percentage—all with instant results.
What is X% of Y?
Multiply Y by X ÷ 100.
Result
30
X is what % of Y?
Divide X by Y, then × 100.
Percentage
25%
Percentage increase / decrease
Change from an old value to a new value.
Percent change
+25%
Increase
Add or subtract percentage
Apply a percent on top of or off a base number.
Result
88
How it works
- X% of Y: multiply Y by X ÷ 100 (e.g. 20% of 50 is 50 × 0.2 = 10).
- X as % of Y: divide X by Y and multiply by 100 (e.g. 15 of 60 is (15 ÷ 60) × 100 = 25%).
- Increase or decrease: use ((new − old) ÷ old) × 100. Positive means growth; negative means a drop.
- Add or subtract %: multiply the number by (1 ± percentage ÷ 100)—add increases the base; subtract reduces it.
FAQ
What is the difference between percentage points and percent change?
Percentage points compare two percentages directly (e.g. 5% to 8% is a 3 percentage point rise). Percent change is relative to a starting value (here, from old to new numbers).
Why can't the "whole" or "from" value be zero?
Dividing by zero is undefined. For "X is what % of Y?", Y must be non-zero. For percent change, the old value must be non-zero so the relative change is meaningful.
How do I increase a price by 10% then decrease it by 10%?
They don't cancel out because the second step uses a new base. Example: 100 + 10% = 110; 110 − 10% = 99. Use this calculator twice, or chain the formulas manually.
Are results rounded?
We format with a reasonable number of decimal places for display. Under the hood, calculations use JavaScript floating-point math; for money or legal use, round using your own rules after copying the value.