Percentage Calculator

Percentages express a number as a fraction of 100. This calculator helps you find a percentage of a value, work out percentage increase or decrease between two numbers, or reverse a percentage to recover the original amount before a change was applied. Everything runs locally in your browser — your inputs are not uploaded to produce the result.

To find a percentage of a number, multiply by the percentage and divide by 100. For example, 20% of 150 is (150 × 20) ÷ 100 = 30. That same idea underpins discounts, tips, commission, and “what is X% of Y?” questions you meet in everyday budgeting.

Percentage increase or decrease compares a new value with an original. Subtract the original from the new value, divide by the original, then multiply by 100. A rise from 80 to 100 is a 25% increase; a fall from 100 to 80 is a 20% decrease. The direction of the change matters — people often mix up “percent of” with “percent change.”

A reverse percentage finds the original value before a percentage was applied. If a price is £120 after a 20% increase, the original was £100 because £120 ÷ 1.2 = £100. The same approach works for VAT-inclusive prices and marked-up costs when you need the pre-change figure.

Use this tool for quick planning on shopping discounts, markups, exam scores, and growth rates. For tax-specific UK VAT add/remove scenarios, the dedicated VAT Calculator may be clearer. Confirm important money decisions with an official source or professional when needed.