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Percentage Calculator

Calculate discounts, shares and percentage changes with a clear formula.

Choose the calculation that matches your question, enter the starting amount and percentage or ending amount, then inspect the formula and result.

For example, 15% of 200 is 30.

Up to 15 integer digits and 6 decimal places. Omit commas, % and units. Use a minus sign for a decrease.

Enable JavaScript to calculate locally in your browser.

How to use

Compare a discount with a price change

Calculate discounts, shares and percentage changes with a clear formula.

Step by step

  1. Provide the source using: Number / Percentage (%).
  2. Set: What would you like to calculate?. Use the reference below to choose the options that fit your task.
  3. Choose: Calculate. Inspect the result before copying, downloading or using it elsewhere.
  4. Choose the calculation that matches your question, enter the starting amount and percentage or ending amount, then inspect the formula and result.

Choosing the settings

OptionWhat changes
What would you like to calculate?A 20% discount on 200 gives 160. Use Increase or decrease with -20. An increase from 200 to 250 is 25%; a decrease from 250 to 200 is 20%, because the starting values differ.
NumberCalculations preserve decimal input precision. Only the displayed result is rounded to at most 6 decimal places, with ties rounded away from zero. Rounded results are marked approximately equal. Amounts are not automatically rounded to two decimal places. Shares can exceed 100%; percentage change requires a positive starting value.

Example and expected result

Increasing 50 by 10% gives 55. Decreasing that 55 by 10% gives 49.5, not 50, because the starting amount changed. This is arithmetic, not a quote including tax, fees or currency conversion.

If it is not working

  • For percentage change, use a positive starting value. Check which amount is the denominator before comparing increases with decreases; rounding a displayed result does not change the original inputs or include taxes and fees.

How do discounts and percentage changes differ?

A 20% discount on 200 gives 160. Use Increase or decrease with -20. An increase from 200 to 250 is 25%; a decrease from 250 to 200 is 20%, because the starting values differ.

How are results rounded?

Calculations preserve decimal input precision. Only the displayed result is rounded to at most 6 decimal places, with ties rounded away from zero. Rounded results are marked approximately equal. Amounts are not automatically rounded to two decimal places. Shares can exceed 100%; percentage change requires a positive starting value.