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.