Percent CompassPercent Compass
About Percent Compass
A clear way to apply a percentage, check a discount, or work backward to the original value.
Start with the right base
Every percentage is a share of a starting value. Percent Compass helps you apply an increase or decrease, calculate a sale price, or find the original value from a known percentage change. The worked examples are illustrative arithmetic examples, not live prices or offers.
Choose, enter, check
Choose a calculation and replace the example numbers with your own. Results update as you type. Switching modes keeps your numbers; Use example loads the example for the selected mode. Clear inputs empties both number fields and keeps your selected mode and direction. Reloading starts again with the increase example.
Inputs and precision
Use zero or positive numbers with a decimal point, without commas, currency symbols, or a percent sign. Scientific notation such as 1e6 is also supported. Decreases and discounts cannot exceed 100%. A 100% decrease cannot be reversed because it does not identify a unique original value. Displayed results are rounded to at most 6 decimal places; very small or large numbers use scientific notation with up to 7 significant digits. Calculations use floating-point arithmetic, so results are approximate. Values outside the supported numeric range are rejected.
Using a result
Open “How it’s calculated” to check the formula and your entered values. Copy result includes the calculation and its precision note. Discount prices use US dollars and exclude taxes, shipping, and fees. Use consistent units in other modes, and check any rounding requirements before using a result for a payment or other important decision.