Percentage Calculator
Calculate percentage of a number, what percentage one value is of another, and percentage change — three calculators in one.
What is X% of Y?
15% of 200
30
After +15%
230
After −15%
170
What % is X of Y?
45 is what % of 180
25.00%
Percentage change from X to Y
Percentage change
+25.00%
increase
How to use this calculator
- Section 1 — Enter a percentage and a number to find that percentage of it, plus values after increase or decrease.
- Section 2 — Enter two numbers to find what percentage the first is of the second (e.g. a score out of a total).
- Section 3 — Enter original and new values for percentage change (e.g. price change).
Three percentage patterns you use every week
Section 1 answers “what is p% of n?”—sales tax, tips as a portion of a subtotal, or progress toward a quota. Section 2 answers “what percent is a of b?”—conversion rates, test scores, margin checks. Section 3 answers relative change—before/after pricing, population deltas, or KPI swings.
Why three modes matter: mixing them mentally causes spreadsheet bugs. Keep units straight: percentage points vs relative percent change are different narratives in finance journalism.
Pairs with the discount calculator for stacked promotions and loan tools for rate impact intuition.
Related tools
These free tools pair well with this page — open them in a new tab to finish your workflow.
Frequently Asked Questions
How do I calculate X% of Y?
Multiply Y by X/100. For example, 15% of 80 = 80 × 0.15 = 12. In the reverse, to find what percentage X is of Y: (X / Y) × 100. For example, 12 is what percent of 80? (12 / 80) × 100 = 15%.
What is percentage increase/decrease?
Percentage change = ((new value − old value) / old value) × 100. A positive result is an increase; negative is a decrease. For example, from 50 to 65: ((65 − 50) / 50) × 100 = 30% increase.
How do I find the original value before a percentage change?
If a value after a P% increase is V, the original = V / (1 + P/100). If after a P% decrease, original = V / (1 − P/100). For example, if a price of £78 is after a 30% increase, the original was 78 / 1.3 = £60.
What is the difference between percentage points and percent?
A percentage point is an absolute difference between two percentages. If the tax rate increases from 20% to 25%, it rose by 5 percentage points (not 5%). The relative percentage change would be (5/20) × 100 = 25%.
How do I add a percentage to a number?
Multiply the number by (1 + percentage/100). To add 20% to 150: 150 × 1.20 = 180. To subtract 20%: 150 × 0.80 = 120.