Reverse Percentage Calculator
Find the original value before a percentage increase or decrease was applied, handy for working backwards from a sale price or tax-inclusive figure.
Your results
Calculation breakdown
- Original value
- Final value ÷ (1 ± Percentage ÷ 100)
Worked example
A jacket now costs $90 after a 10% discount. Reversing this: $90 ÷ (1 − 0.10) = $100 was the original price.
Assumptions
- Percentage decreases of 100% or more cannot be reversed since the original value would be undefined.
- Enter the percentage as a positive number and choose the direction it moved.
How this calculator works
This calculator works backwards from a final value and a known percentage change to find the original amount. Enter the resulting number and whether it went up or down by a given percentage, and it reverses the maths to show the starting figure.
Frequently asked questions
How do I use this for a discounted price?
Enter the sale price you paid, select 'decrease' and enter the discount percentage to find the original price before the discount.
Can I use it for GST-inclusive prices?
Yes, enter the GST-inclusive price, choose 'increase' and enter 10% to find the GST-exclusive amount.
What happens if the percentage is 100% decrease?
A 100% decrease implies the original value was infinite unless the final value is zero, so the calculator returns an error for that edge case.
Editorial review and responsibility
Reviewed by the CalcAussie editorial team on 21 September 2026. Review scope: Method, Australian terminology, material assumptions, source links and user-facing limitations.
Calculator results remain estimates based on the figures entered. Check material decisions against current official information and report a suspected error so it can be reproduced and corrected.