Percentage Calculator
Free percentage calculator — percent of a number, percentage increase, percentage decrease, percent change, and X is what % of Y.
Everyday Uses
Shopping discounts
Work out the final price of a "30% off" deal in seconds — and stack a second discount correctly.
Tipping
Split a restaurant bill and add 15–20% without mental gymnastics.
Raises and price changes
Turn "your rent is going up $150" into a percentage — or a "4% raise" into actual dollars.
Test scores
Convert 43 out of 55 marks into a percentage grade instantly.
Frequently Asked Questions
How do I find what percentage one number is of another?
Divide the part by the whole, then multiply by 100. Formula: (Part ÷ Whole) × 100. Example: 45 is what % of 180? → (45 ÷ 180) × 100 = 25%. This is the most common percentage calculation for test scores, tips, and discounts.
How do I calculate percentage increase or decrease?
Percentage change = ((New Value − Old Value) ÷ Old Value) × 100. A positive result means an increase; negative means a decrease. Example: price rises from $80 to $92 → ((92 − 80) ÷ 80) × 100 = +15% increase.
How do I calculate X% of a number?
Multiply the number by the percentage divided by 100. Formula: Number × (Percentage ÷ 100). Example: 15% of $240 = 240 × 0.15 = $36. Quick mental trick: 15% = 10% + 5%. 10% of 240 is 24, half of that is 12, so 24 + 12 = $36.
How do I reverse a percentage to find the original number?
Divide the final value by (1 + percentage/100). Example: after a 20% increase a price is $120 — the original was $120 ÷ 1.20 = $100. For a decrease: if a price fell 25% to $75, original = $75 ÷ 0.75 = $100.
What is the difference between percentage points and percent change?
Percentage points are an absolute difference between two percentages. Percent change is relative. If interest rates go from 2% to 3%, that is +1 percentage point, but a +50% relative increase. Politicians often swap these terms — always check which is being used.
How do you calculate a percentage increase?
Multiply the starting value by the percentage, then add it back: 1,200 increased by 15% is 1,200 + (1,200 x 0.15) = 1,200 + 180 = 1,380. The shortcut is to multiply by 1.15 directly (100% + 15%). Use this for raises, markups, rent rises, and tips.
How do you calculate a percentage decrease?
Multiply the starting value by the percentage, then subtract it: 1,200 decreased by 15% is 1,200 - 180 = 1,020. The shortcut is to multiply by 0.85 (100% - 15%). Use this for discounts, price drops, and reductions. Note that a decrease of more than 100% is impossible - it would take the value below zero.
Why is a 15% increase then a 15% decrease not back to the start?
Because each percentage applies to a different base. 1,200 increased by 15% is 1,380; decreasing 1,380 by 15% subtracts 207 (15% of the larger number), landing at 1,173 - not 1,200. This is why a 50% loss needs a 100% gain to recover, and it catches people out constantly in investing and retail pricing.