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Percentage Calculator

Three calculators in one: what is X% of Y, X is what percent of Y, and percentage change between two numbers. Type two numbers, get the answer.

Result
20

Percentages show up everywhere — discounts, tips, tax, grades, raises — and they cause a surprising number of mistakes because "percent" just means "per hundred" and people forget which number goes where. This calculator covers the three questions people actually ask, each with the formula shown so you can check the work.

Type the two numbers into the matching mode and the answer appears instantly, with the steps written out. No sign-up, no ads in the way, and it works fine on a phone held one-handed in a shop aisle.

Part of the Everyday Calculators collection on CountCrunch.

The three percent problems

X% of Y = (X ÷ 100) × YX is what % of Y = (X ÷ Y) × 100% change = ((new − old) ÷ old) × 100

Worked examples

  • 20% of 85 = 0.20 × 85 = 17. That is your tip on an $85 bill.
  • 45 is what % of 180? = 45 ÷ 180 × 100 = 25%. You scored 45 out of 180.
  • Price rose from $40 to $46: (46 − 40) ÷ 40 × 100 = 15% increase.
  • Price fell from $80 to $60: (60 − 80) ÷ 80 × 100 = −25%, a 25% decrease.

Mental shortcuts worth knowing

  • 10%: move the decimal one place left (10% of 240 = 24). Halve it for 5%, double for 20%.
  • Reverse percentages: X% of Y equals Y% of X. 8% of 50 is the same as 50% of 8 = 4 — much easier.
  • Percentage points vs percent: going from 20% to 25% is a 5 percentage point rise but a 25% relative increase. Politicians and advertisers mix these up constantly.

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100, then multiply by the number. 15% of 200 = 0.15 × 200 = 30.

How do I find what percent one number is of another?

Divide the first number by the second and multiply by 100. 30 is what percent of 120? 30 ÷ 120 × 100 = 25%.

How do I calculate percentage increase?

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

What is the difference between percent and percentage points?

Percent is relative; percentage points are absolute. A rate rising from 10% to 12% gained 2 percentage points, which is a 20% relative increase.

How do I reverse a percentage? (e.g. price before 20% off was $80)

Divide by (1 − discount). $80 ÷ 0.80 = $100 was the original price. For adding: divide by (1 + rate).

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