Make sense of everyday numbers

PercentFox is a growing set of clear, trustworthy calculators. Every result comes with the answer, what it means in plain English, and how it was worked out. Start with the percentage calculator below.

Percentage CalculatorWhat is X% of Y, X is what % of Y, and X is Y% of what number.Percentage Change CalculatorThe percent change between two values, and applying an increase or decrease.Percentage Difference CalculatorHow far apart two values are, relative to their average — order doesn't matter.Reverse Percentage CalculatorA value went up or down by a percent — find what it was before the change.Percentage Point CalculatorThe gap between two rates in percentage points, and the relative percent change.Discount CalculatorA sale price and how much you save — enter a price and a percent off.Profit Margin CalculatorYour margin from a price and a cost, or the price for a target margin — and how margin differs from markup.ROI CalculatorReturn on investment from an amount invested and an amount returned — and why the same profit is a different ROI at a different investment size.

Common percentage problems

What is 20% of 150?30 is what percent of 120?$40 rose to $55 — what percent?$500 increased by 12%$80 with 25% offMargin on $100 revenue, $60 cost$1,000 invested, $1,250 back — what ROI?What was it before rising 20% to 120?20% to 25% — points or percent?How far apart are 10 and 6?

Which calculator should I use?

Your questionUseFormula
What is 20% of 150?Percentage Calculator(P / 100) × whole
45 is what percent of 60?Percentage Calculatorpart / whole × 100
Price went from $80 to $100 — what percent?% Change(end − start) / |start| × 100
What is $500 plus 12%?% Change → Increase / Decreasebase × (1 + P / 100)
What is $80 minus 25%?% Change → Increase / Decreasebase × (1 − P / 100)
What's the sale price at 25% off $80?Discountprice × (1 − P / 100)
Sell at $100, cost $60 — what's the margin?Profit Margin(revenue − cost) / revenue × 100
Put in $1,000, got $1,250 back — what return?ROI(returned − invested) / invested × 100
120 after a 20% rise — what was it before?Reverse %final / (1 + P / 100)
Is 20% → 25% five points or 25%?% Pointto − from (and ÷ from for the %)
How far apart are 10 and 6?% Difference|a − b| / ((a + b) / 2) × 100

Percentage basics

A percentage is a number expressed as a fraction of 100. The word comes from the Latin per centum, “by the hundred.” So 25% means 25 out of 100, or the fraction 25/100, or the decimal 0.25. To convert a decimal to a percentage, multiply by 100; to go the other way, divide by 100.

Percentages can be larger than 100% (the part is bigger than the whole) and can be negative (a decrease). “Percentage points” are not the same as “percent”: a rate moving from 10% to 12% is a rise of 2 percentage points, but a 20% increase in the rate itself.

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For 20% of 150: 20 / 100 = 0.2, then 0.2 x 150 = 30.

How do I work out what percentage one number is of another?

Divide the first number by the second and multiply by 100. 45 out of 60 is 45 / 60 x 100 = 75%.

Is percentage change the same as percentage difference?

No. Percentage change measures a move from an earlier value to a later one and has a direction (up or down). Percentage difference compares two values with no before/after and divides by their average, so the order does not matter.

Do the calculators store what I type?

No. Every calculation runs in your browser. The numbers you enter are not sent anywhere or saved.

Why PercentFox is different

Most calculators stop at a number. PercentFox adds a plain-English reading of that number, shows the formula with your values filled in, and — when there’s something genuinely useful to add — a short Fox Insight. Percentages are where PercentFox starts, not where it ends.