Reverse Percentage Calculator
Find the original amount before a percentage change. e.g. “$84 is after 30% off, what was the original?”
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Results update as you type. All calculation happens in your browser.
Methodology
Find the original amount before a percentage change. This tool uses a standard, documented formula and runs entirely on your device.
Last reviewed January 2026 · Runs client-side
Working back to an original amount
Reverse percentages answer a question ordinary percentage math cannot: given a figure after a change, what was it before? It comes up whenever you need the price before a discount, the total before tax, or the salary before a raise.
The trap is that you divide rather than add the percentage back, a distinction this calculator handles for you in both directions.
How to use this calculator
- Enter the amount you have after the change.
- Set the percentage that was applied.
- Choose whether that amount was reduced or increased, then read the original.
What the inputs mean
- The amount was
- “Reduced” for a discount or drop; “Increased” for a raise, markup, or added tax.
- Percentage
- The size of the change that was applied to the original figure.
An $84 item after 30% off had an original price of $84 ÷ 0.7 = $120, not $84 plus 30%, which would give the wrong answer.
The formula, in plain terms
Divide the amount by one minus the percentage for a reduction, or by one plus the percentage for an increase.
Frequently asked questions
Why divide instead of adding it back?
Because the change was calculated on the original, larger or smaller figure. Only division recovers that starting value correctly.
Can I use this to remove tax?
Yes. Choose “Increased” and enter the tax rate to work back to the pre-tax amount.
Last reviewed January 2026. This explainer is general information, not professional advice.