Arithmetic • Instant Results
Percentage Calculator
Calculate percentages, increases, decreases, and more — instantly.
What is X% of Y?
40 is 20% of 200
X is what % of Y?
20% 40 is 20% of 200
Percentage Increase / Decrease
20% increase from 100 to 120
Frequently Asked Questions
How do I calculate a percentage?
To find X% of Y, multiply Y by X/100. For example, 20% of 200 = 200 × 0.20 = 40.
How do I calculate percentage increase?
Percentage increase = ((New - Original) / Original) × 100. For example, from 100 to 120 = ((120-100)/100) × 100 = 20%.
What This Percentage Calculator Does
This tool covers the three most common percentage problems: finding what X% of a number is, finding what percent one number is of another, and finding the percentage increase or decrease between two values. Enter your numbers and every result updates instantly, with the formula shown alongside the answer.
How It Works
X% of Y = Y × (X / 100) — multiply the whole number by the percentage expressed as a decimal.
X is what % of Y = (X / Y) × 100 — divide the part by the whole, then convert to a percentage.
Percentage change = ((New − Original) / Original) × 100 — a positive result is an increase, a negative result is a decrease.
Common Uses
Percentage calculations show up constantly in everyday finance and shopping: figuring out a discount at checkout, calculating a tip, comparing this year's rent to last year's, or checking how much a paycheck grew after a raise. Because the math is the same three formulas every time, this calculator is built to answer all of them in one place.
Frequently Asked Questions
How do I calculate a percentage?
To find X% of Y, multiply Y by X divided by 100. For example, 20% of 200 is 200 × 0.20 = 40.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100. Going from 100 to 120 is ((120-100)/100) × 100 = 20% increase.
What's the difference between percentage points and percent change?
Percentage points measure the raw difference between two percentages (e.g. 40% to 50% is a 10 percentage-point increase), while percent change measures the relative change (that same move is a 25% increase, since 10/40 = 25%). Mixing the two up is a common source of confusion in news and financial reporting.
How do I reverse a percentage calculation to find the original number?
If you know the result and the percentage, divide the result by the percentage (as a decimal). For example, if 40 is 20% of a number, the number is 40 / 0.20 = 200.