Percentage Calculator
Calculate discounts, shares and percentage changes with a clear formula.
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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.
Compare a discount with a price change
Choose the calculation that matches your question, enter the starting amount and percentage or ending amount, then inspect the formula and result.
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.