Reverse Percentage Calculator
Enter the final value, percentage rate, and whether the percentage was added or subtracted. The calculator works backward to estimate the original value.
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The result is the estimated value before the selected percentage adjustment. Reapply the adjustment to check that it returns the entered current value.
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How to Use This Calculator
Enter the current value and a percentage below 100%, then select whether the percentage was subtracted or added.
Formula & Methodology
After a discount or reduction: Original = Current ÷ (1 − Rate ÷ 100). After a markup, tax, or increase: Original = Current ÷ (1 + Rate ÷ 100).
Examples: discount and markup
$80 after a 20% discount came from an original value of $100. $120 after a 20% markup also came from an original value of $100.
The percentage input is limited to less than 100% so both calculation branches remain valid in the shared formula engine. This version therefore does not model markups of 100% or more. It assumes one percentage was applied directly to the original value.
This is a general mathematical estimate. Real invoices, taxes, discounts, fees, and rounding rules may apply percentages in a different order.
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Related Guides
- How Percentages Work: Complete Guide with ExamplesUnderstand percentages from the ground up. Covers what percent means, basic percentage calculations, percentage increase and decrease, and common real-world uses.
- Reverse Percentage Explained: Find the Original Value Before a % ChangeLearn how to calculate the original value before a percentage increase or decrease. Covers the reverse percentage formula with worked examples in prices, discounts, and taxes.
- What Is Percentage Increase? Formula, Examples, and Common UsesUnderstand percentage increase: the formula, how to calculate it step by step, and real-world examples in prices, salaries, and test scores. Includes common mistakes to avoid.
- Percentage Difference vs. Percentage Change: What's the Difference?Percentage difference and percentage change are not the same thing. Learn when to use each, how to calculate both, and why the distinction matters in data analysis and everyday math.
- How to Calculate Percentages Without a Calculator: Mental Math MethodsLearn to calculate percentages in your head using simple strategies: the 10% shortcut, doubling/halving, and breaking percentages into parts. Works for tips, discounts, and sales.
Frequently Asked Questions
- How do I find the original price before a discount?
- Divide the discounted price by one minus the discount rate as a decimal. For example, $80 ÷ 0.80 = $100.
- How do I find a value before tax or markup?
- Divide the final value by one plus the added rate as a decimal. For example, $120 ÷ 1.20 = $100.
- Why can’t I simply add the percentage back?
- The percentage was applied to the original value, not the final value, so adding the same percent to the final value uses the wrong base.
- Why is the rate limited to less than 100%?
- The percentage input is limited to less than 100% because reversing a 100% discount is mathematically undefined. This calculator assumes one percentage adjustment was applied directly to the original value and does not model multiple discounts, taxes, fees, or compounded changes.
Last updated 7/17/2026