Percentage Calculator
Three modes: X% of Y, X is what % of Y, and % change.
What is% of?= 50
is what % of?= 25%
% change fromto= +50%
What It Does
Three calculation modes in one tool. Find a percentage of a number (tip amounts, discounts), determine what percentage one value is of another (scores, ratios), or calculate the percentage change between two values (price changes, growth rates). All results update instantly as you type.
Percentage Formulas
Everyday Examples
Common Mistakes to Avoid
Frequently Asked Questions
- How do I calculate what percentage one number is of another?
- Divide the part by the whole and multiply by 100. Formula: (part ÷ whole) × 100 = percentage. For example, 45 is what percent of 180? (45 ÷ 180) × 100 = 25%. Use the "X is what % of Y" mode in this calculator.
- How do I calculate percentage change (increase or decrease)?
- Percentage change = ((New Value − Old Value) ÷ |Old Value|) × 100. A positive result is an increase, a negative result is a decrease. Example: price changed from $80 to $100 → ((100 − 80) ÷ 80) × 100 = 25% increase.
- How do I find X% of a number?
- Multiply the number by X and divide by 100. Formula: (X ÷ 100) × Y. Example: what is 15% of 240? (15 ÷ 100) × 240 = 36. A quick mental shortcut: 10% is moving the decimal left once, then adjust from there.
- How do I reverse a percentage — find the original value before a percentage was applied?
- Divide the final value by (1 + rate) for increases, or (1 − rate) for decreases. Example: a price of $115 includes 15% tax — original = 115 ÷ 1.15 = $100. For a 20% discount: if sale price is $80, original = 80 ÷ 0.80 = $100.
- What is the difference between percentage points and percent change?
- Percentage points (pp) measure an absolute difference between two percentages. If interest rates rise from 2% to 5%, that is 3 percentage points but a 150% relative increase. Confusing the two is a common error in financial and statistical reporting.