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Percentage Calculator

Solve the four everyday percentage problems — percent of, what percent, percent change and original value.

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How to use Percentage Calculator

  1. 1Find the question that matches your problem — each row is a sentence with blanks.
  2. 2Type your numbers into the boxes in that row.
  3. 3The answer appears instantly on the right. Increases show in green and decreases in red.
  4. 4Click Copy to use the result elsewhere.

Four percentage calculators in one

Percentages appear everywhere — discounts, tips, tax, exam scores, interest rates, statistics and price changes — but it is easy to mix up which number to divide by. This percentage calculator solves the four most common questions side by side. Each row reads like a sentence, so you simply fill in the blanks and read the answer. All calculations happen instantly in your browser.

What each row calculates

What is X% of Y? The basic percentage of a number: a 15% tip on a 64.00 bill, 20% VAT on a price, or 30% of a budget. Formula: X ÷ 100 × Y.

X is what percent of Y? Turns a fraction into a percentage: test scores, completion rates, market shares or the proportion of a budget already spent. Formula: X ÷ Y × 100.

Percentage change from X to Y. Shows growth or decline: price rises, salary increases, website traffic, weight loss or investment returns. Positive results are increases, negative results decreases. Formula: (Y − X) ÷ |X| × 100.

X is Y% of what? Works backwards to the whole: the original price before a discount, the total when you know one share, or a full amount from a deposit. Formula: X ÷ Y × 100.

Everyday examples

  • Shopping: a jacket costs 120 with 25% off. 25% of 120 is 30, so you pay 90. To find the discount percentage from prices, use the change row: 120 → 90 is −25%.
  • Tips: 18% of a 47.50 bill is 8.55.
  • Grades: 54 correct answers out of 72 is 75%.
  • Salary: a raise from 3,200 to 3,440 per month is a 7.5% increase.
  • Sales tax: if a receipt shows tax of 6.40 at 8%, the pre-tax amount was 80.

Common percentage mistakes

Using the wrong base. Percentage change always divides by the starting value. A rise from 80 to 100 is +25%, but a fall from 100 to 80 is −20%.

Adding percentages that apply in sequence. Two successive 10% discounts are not 20% off: 100 → 90 → 81, which is 19% off in total.

Confusing percent and percentage points. Going from 4% to 5% unemployment is a 1-point rise, but a 25% relative increase.

For loan repayments and interest, use the Loan Calculator.

Frequently asked questions

How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 80 = 0.15 × 80 = 12. Use the first row of the calculator.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. If you scored 42 out of 60, that is 42 ÷ 60 × 100 = 70%. Use the second row.
How is percentage change calculated?
Subtract the old value from the new value, divide by the old value and multiply by 100. A price going from 50 to 65 is (65 − 50) ÷ 50 × 100 = +30%. A drop from 65 to 50 is −23.08% — not −30%, because the starting value is different.
How do I find the original number if I know a percentage of it?
Divide the known amount by the percentage and multiply by 100. If 30 is 20% of a number, the number is 30 ÷ 20 × 100 = 150. This is how you find a pre-sale price or a total from a share.
What is the difference between percent and percentage points?
If an interest rate rises from 2% to 3%, it has risen by 1 percentage point, but by 50 percent relative to where it started. News and finance often confuse the two.
Why does a 50% decrease followed by a 50% increase not return to the start?
Each percentage applies to a different base. 100 − 50% = 50, then 50 + 50% = 75. To undo a 50% decrease you need a 100% increase.

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