Calculate percentages easily — discounts, tips, percentage increases and decreases. Free online percentage calculator wi...
Percentages are everywhere in daily life — from calculating discounts while shopping to figuring out tips at restaurants, understanding salary raises, and analyzing data changes. Our percentage calculator handles three essential calculation types: finding a percentage of a number (What is 20% of 350?), calculating percentage increase (Your salary went from $3000 to $3500 — what percent increase is that?), and calculating percentage decrease. Each result includes a step-by-step breakdown showing exactly how the math works, making it an educational tool as well as a practical calculator.
Find percentage of a number, calculate percentage increase, percentage decrease, and what percent one number is of another.
Yes, we include one-click buttons for common percentages like 5%, 10%, 15%, 20%, 25%, and 50%.
Yes, every result shows the step-by-step math breakdown so you can understand how it works.
Yes, completely free for everyone including students, teachers, and professionals.
Percentages are the arithmetic of everyday decisions — discounts, tips, taxes, interest, grades, statistics. Yet they hide more traps than almost any other basic math, from reversed discounts to the difference between percent and percentage points. This guide covers the three core problem types this calculator solves, worked examples for each, and the mistakes that cost people real money.
1. What is X% of Y? Multiply: X ÷ 100 × Y. Example: 15% of 240 = 0.15 × 240 = 36. This handles tips, commissions, and tax amounts.
2. X is what percent of Y? Divide and scale: X ÷ Y × 100. Example: 45 of 180 = 45 ÷ 180 × 100 = 25%. This converts scores, market shares, and completion rates into comparable figures.
3. Percentage change from A to B: (B − A) ÷ A × 100. Example: a price moves from 80 to 92 → (92 − 80) ÷ 80 × 100 = +15%. Crucially, the denominator is the original value — the single most common source of wrong answers.
Given a final price that already includes a change, undo it by dividing, not subtracting. A jacket costs $85 after a 20% discount: the sale price is 80% of the original, so the original was 85 ÷ 0.80 = $106.25 — not 85 + 20% = 102. Same for tax: a $120 total that includes 20% VAT contains 120 ÷ 1.20 = $100 base and $20 tax. Whenever the percentage was applied to an unknown original, division by (1 ± rate) recovers it.
Fast approximations make you dangerous in a good way. 10% is one decimal shift (10% of 340 = 34); 5% is half that; 1% is two shifts. Compose them: 15% tip on $62 → 6.20 + 3.10 = $9.30. The commutative trick often simplifies: 8% of 25 equals 25% of 8 = 2, computed instantly. For quick growth estimates, the Rule of 72: money at r% compound interest doubles in roughly 72 ÷ r years — 6% doubles in ~12 years.
Shopping: verifying that a "was/now" tag matches the advertised percentage. Dining: tipping 15–20% without a phone pause. Finance: converting a monthly fee into an annual percentage of your balance, or checking a raise against inflation (a 3% raise during 4% inflation is a real-terms pay cut of about 1%). Health and fitness: tracking body-weight change or macro splits. School and work: turning any score into a percent, and any percent back into the underlying numbers when the base matters.