🧮 Percentage Calculator
Calculate any percentage — discounts, changes, ratios — instantly.
Our free Percentage Calculator handles the three most common percentage problems: what is X% of Y, X is what percent of Y, and what is the percentage change from X to Y. Essential for discounts, taxes, tips, grades, financial changes, and everyday math.
Three Core Percentage Formulas
X is what % of Y? → Percentage = (X ÷ Y) × 100
% change from X to Y? → Change = ((Y − X) ÷ X) × 100
Common Examples
Discount: 30% off $85 → $85 × 0.30 = $25.50 off → you pay $59.50
Sales tax: $120 plus 8.5% tax → $120 × 1.085 = $130.20
Test score: 42 correct out of 56 → (42 ÷ 56) × 100 = 75%
Revenue growth: $150K to $210K → ((210-150) ÷ 150) × 100 = +40%
Commission: 5% on $18,000 sale → $18,000 × 0.05 = $900
Common Percentage Mistakes to Avoid
Stacked discounts are not additive: A 30% discount followed by an additional 20% off is NOT 50% off. $100 × 0.70 = $70, then $70 × 0.80 = $56. Total discount = 44%, not 50%.
Percentage change is not symmetric: If a price rises 20% then falls 20%, you do not break even. $100 → $120 → $96. You're 4% below where you started.
Back-calculating tax: To find the pre-tax price from a total including tax, divide by (1 + tax rate). A $108 total with 8% tax: $108 ÷ 1.08 = $100 pre-tax. Many people incorrectly subtract 8% from $108, getting $99.36.
Percentage Points vs Percentages
A critical distinction often confused in finance and statistics: if an interest rate rises from 3% to 5%, it rose by 2 percentage points, but it increased by 66.7% (since 2/3 = 0.667 = 66.7%). Political polls and financial reporting often use percentage points when discussing changes in rates or proportions.
🧮 Calculate any percentage instantly with our free Percentage Calculator.
Open Calculator →Frequently Asked Questions
How do I calculate a percentage increase?
Percentage increase = ((New Value − Old Value) ÷ Old Value) × 100. If sales went from $50,000 to $65,000: ((65,000 − 50,000) ÷ 50,000) × 100 = 30% increase.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. If 35 students passed out of 50: (35 ÷ 50) × 100 = 70%. 35 is 70% of 50.
How do I reverse a percentage (find the original before a % increase)?
Divide the final amount by (1 + the percentage as a decimal). If a price is $130 after a 30% increase: $130 ÷ 1.30 = $100 original price.