Mathematical Formula & Method
Reverse Percentage Calculator Formula
Original = Final / (1 + Rate/100) for increase | Original = Final / (1 − Rate/100) for decrease
Worked Examples & Step-by-Step Solutions
$118 after 18% tax increase
- Multiplier: 1 + 0.18 = 1.18.
- Original: 118 / 1.18 = $100.00.
How to Use the Reverse Percentage Calculator
- Enter final amount and percent change to deduce the original baseline value.
Important Assumptions & Unit Conventions
- Avoid subtracting the percentage from the final value, which is a common math error.
Frequently Asked Questions
Why can’t I just subtract 20% from a discounted price to get the original?
Because 20% was calculated based on the original number, not the discounted number!
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