Calculate any percentage problem instantly. What is X% of Y, percentage change, increase, decrease, and reverse percentage — all in one place.
A percentage is a number expressed as a fraction of 100. The word comes from the Latin per centum, meaning "by the hundred." Percentages are used everywhere — from calculating discounts and tax, to measuring growth rates, exam scores, and salary increases.
To find a percentage of a number, multiply the number by the percentage and divide by 100.
Example: What is 20% of 150? → (20 ÷ 100) × 150 = 30
To find what percentage one number is of another, divide the first by the second and multiply by 100.
Example: What percentage is 30 of 150? → (30 ÷ 150) × 100 = 20%
To calculate the percentage change between two values, subtract the old value from the new, divide by the old value, and multiply by 100. A positive result is an increase, a negative result is a decrease.
Example: Price went from £80 to £100 → ((100 − 80) ÷ 80) × 100 = 25% increase
Percentage calculations that work together with this tool:
→ Discount Calculator — Calculate sale prices, percent off, reverse discount and stacked discounts.
→ VAT Calculator — Calculate VAT and GST for 27+ countries. Add or remove tax from any price.
→ Profit Margin Calculator — Calculate gross, net and operating profit margins for your business.
→ Tip Calculator — Calculate gratuity at restaurants, for delivery and more with a split bill feature.
Percentages appear in nearly every domain of daily and professional life — discounts, tax rates, investment returns, exam scores, salary changes, and probability. Understanding the five core percentage calculation types eliminates the need to guess which formula to use.
15% of $80 = $80 × 0.15 = $12. Mental shortcut: 10% is moving the decimal point left by one place, then adjust from there.
25 is what % of 80? = (25/80) × 100 = 31.25%. Used for test scores, market share, and budget percentages.
$50 to $65: ((65-50)/50) × 100 = 30% increase. Always divide by the original value, not the new one.
To increase by X%: multiply by (1 + X/100). To decrease: multiply by (1 - X/100). Increase $200 by 15%: $200 × 1.15 = $230.
If $65 is after a 30% increase: $65 / 1.30 = $50 original. If $48 is after a 20% discount: $48 / 0.80 = $60 original price.
Stacked discounts cannot be added together: 30% off then 10% off is 37% off, not 40%. A 50% increase followed by a 50% decrease does not return to the original — you end up at 75% of the start. Percentage points and percent change are different: if rates rise from 3% to 5%, they increased by 2 percentage points but by 66.7% relative to the original. Percentage change must be calculated against the old value, not the new one. Confusing markup and margin leads to systematic under-pricing — a 50% markup is 33.3% margin, not 50% margin.