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Percentage Calculator

Calculate percentages in three different ways — instantly.

Input

%

Result

Result
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Frequently Asked Questions

Multiply the number by the percentage, then divide by 100. Example: 15% of 200 = 200 × 15 ÷ 100 = 30.
Percentage change = ((New − Old) ÷ |Old|) × 100. From 80 to 100 is +25%; from 100 to 80 is −20%.
Divide the part by the whole and multiply by 100. Example: 30 as a % of 200 = 30 ÷ 200 × 100 = 15%.

How to Calculate Percentages

A percentage is simply a number expressed as a fraction of 100. The word itself comes from the Latin "per centum" — meaning "by the hundred". When you see 25%, it means 25 out of every 100, or 0.25 as a decimal.

Three Common Percentage Calculations

Finding X% of a number: Multiply the number by the percentage divided by 100. For example, 15% of 200: 200 × 0.15 = 30. This is useful for calculating tips, discounts, tax amounts, and pay rises.

What percentage is X of Y: Divide X by Y and multiply by 100. For example, what percentage is 45 of 180? 45 ÷ 180 × 100 = 25%. This is useful for exam scores, conversion rates, and comparing values.

Percentage change: ((New − Old) ÷ |Old|) × 100. For example, a price goes from £80 to £100: (100 − 80) ÷ 80 × 100 = 25% increase. If it goes from £100 to £80: (80 − 100) ÷ 100 × 100 = −20% decrease. Note that a 25% increase followed by a 20% decrease brings you back to the same number — percentage changes aren't symmetrical.

Worked Example: Pay Rise

Your salary is £28,000 and you're offered a 4% pay rise. Using the "X% of Y" calculation: £28,000 × 0.04 = £1,120. Your new salary is £29,120. To check: use the salary calculator to see how much extra take home pay that gives you after tax.

Common Percentage Mistakes

The most common mistake is treating percentage increases and decreases as symmetrical. A 50% increase followed by a 50% decrease does NOT get you back to the original number. £100 + 50% = £150, then £150 − 50% = £75. You've lost £25. This is why the percentage change calculator is so useful — it prevents these errors.

Related Calculators

The discount calculator applies percentage-off calculations to shopping. The VAT calculator adds or removes percentage-based tax. And the tip calculator works out percentage-based gratuities.

KwikSum's percentage calculator handles three common operations: finding X% of any number, expressing one number as a percentage of another, and calculating the percentage change between two values. Results update in real time as you type — no need to press calculate.