AbacusKitCalculators & tools
AbacusKit · https://abacuskit.com/global/percentage/ · 2026-10-22

Percentage Calculator

20 % of 150 is 30. Pick what you want to find, type two numbers, done.

What do you want to find?
First value (x)
Second value (y)

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How it works

Pick what you want to find, type the two numbers, and read the result. The three modes cover almost every everyday percentage question:

  • X % of Y — discounts, tips, VAT, interest for one period.
  • X is what % of Y — test scores, market share, progress towards a goal.
  • % change from X to Y — price rises, salary increases, year-on-year growth.

Results are shown with full precision; round them yourself as needed. The calculator refuses inputs that would divide by zero and tells you which number to change.

Formula and worked example

Mode Formula Example
X % of Y Y × X ÷ 100 20 % of 150 = 30
X is what % of Y X ÷ Y × 100 45 of 180 = 25 %
% change from X to Y (Y − X) ÷ |X| × 100 80 → 100 = 25 %

Step by step for a 19 % VAT amount on a €1,234.56 net price:

  1. Convert the percentage to a decimal: 19 ÷ 100 = 0.19
  2. Multiply: 1,234.56 × 0.19 = 234.57
  3. Round to cents for an invoice: €234.57

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 20 % of 150 is 150 × 20 ÷ 100 = 30.

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

Divide the part by the whole and multiply by 100. 45 out of 180 is 45 ÷ 180 × 100 = 25 %.

How is percentage change calculated?

Subtract the starting value from the new value, divide by the starting value, and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25 %. A fall gives a negative result.

What is the difference between percent and percentage points?

Percent compares one value with another. Percentage points measure the plain difference between two percentages. If a rate moves from 4 % to 5 %, that is a rise of 1 percentage point, but a 25 % increase.

Why does a 50 % drop need a 100 % rise to recover?

Because percentage change is always measured from the starting value. Falling from 100 to 50 is −50 %. Rising from 50 back to 100 is +100 %, since 50 is the new base.

Can I calculate a percentage of a negative number?

Yes. The sign carries through. 10 % of −80 is −8. For percentage change from a negative start, the calculator measures the change against the absolute value of the starting number so the sign shows the direction.

Sources and methodology

Last updated 2026-10-19. Calculator version 1.0.0.Read how we calculate for our verification process.

Results are estimates for information only and are not financial, tax or legal advice.