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Percentage Calculator

A percentage is a number out of 100. To find a percentage of a number, multiply the number by the percentage and divide by 100: 20% of 150 is 150 × 20 ÷ 100 = 30. Use the four calculators below to find a percentage of a number, what percent one number is of another, the original number, or the percentage change between two values.

What is X% of Y?

X is what percent of Y?

X is Y% of what?

Percentage change from X to Y

How to use the percentage calculator

  1. Pick the calculator that matches your question. Use the links at the top to jump straight to it.
  2. Enter your two numbers. Decimals and negative numbers work, and you can leave out the % sign.
  3. Press Calculate to see the answer, a plain-English sentence you can copy and the full working.

Percentage formulas

X% of Y = Y × X ÷ 100

X as a percent of Y = X ÷ Y × 100

The whole when X is Y% = X ÷ (Y ÷ 100)

Percentage change from X to Y = (Y − X) ÷ |X| × 100

|X| means the size of X without its sign, so percentage change works for negative starting values too. A positive change is an increase; a negative change is a decrease.

Worked examples

What is 15% of 80?

80 × 15 ÷ 100 = 12. You can also turn the percentage into a decimal first: 80 × 0.15 = 12.

45 is what percent of 150?

45 ÷ 150 = 0.3, and 0.3 × 100 = 30%.

30 is 20% of what number?

20% as a decimal is 0.2, and 30 ÷ 0.2 = 150.

Percentage change from 80 to 60

(60 − 80) ÷ 80 × 100 = −25, so it’s a 25% decrease.

Percent vs. percentage points

Percentage points measure the gap between two percentages. Percent measures relative change. If an interest rate rises from 4% to 5%, it has gone up by 1 percentage point, but that’s a 25% increase in the rate itself. News reports mix these up all the time.

Why a 50% rise and a 50% fall don’t cancel out

Each percentage applies to a different starting value. $100 up 50% is $150, but $150 down 50% is $75, not $100. That’s why a stock that falls 50% needs to rise 100% to get back to where it started.

When you’d actually use a percentage calculator

  • Doing the tip math before the server comes back. 20% of a $86 dinner is $17.20, so you can round up with confidence instead of guessing.
  • Checking whether that “40% off” sale is real. If the sale price is $60 and that’s 60% of the original, the original was $100. Now you know whether the tag was telling the truth.
  • Grading the group project fairly. If you did 18 of the 24 slides, you did 75% of the work. Bring receipts.

How we calculate

Each calculator uses the standard formula shown above, calculated at full precision and rounded to at most four decimal places for display. Percentage change divides by the size of the starting value, so it works with negative numbers, and it can’t be calculated from a starting value of zero. Finding what percent X is of Y needs a total that isn’t zero, and finding the whole needs a percentage that isn’t zero.

Frequently asked questions

What is the formula for percentage?

Percentage = (part ÷ whole) × 100. For example, 45 out of 150 is 45 ÷ 150 × 100 = 30%.

How do I calculate a percentage of a number?

Multiply the number by the percentage, then divide by 100. 15% of 80 is 80 × 15 ÷ 100 = 12. You can also convert the percentage to a decimal first: 80 × 0.15 = 12.

How do I calculate a percentage increase?

Subtract the starting value from the new value, divide by the starting value and multiply by 100. From 50 to 65 is (65 − 50) ÷ 50 × 100 = a 30% increase.

How do I calculate a percentage decrease?

Use the same formula. The result is negative for a decrease: from 80 to 60 is (60 − 80) ÷ 80 × 100 = −25%, which is a 25% decrease.

How do I find the original number from a percentage?

Divide the known amount by the percentage written as a decimal. If 30 is 20% of a number, the number is 30 ÷ 0.20 = 150.

What is the difference between percent and percentage points?

Percentage points measure the gap between two percentages, while percent measures relative change. A rate rising from 4% to 5% is up 1 percentage point, which is a 25% increase.