How to find the original price before a discount
Updated on June 30, 2026 · by Rafael Rossi
Reverse percentage answers "what was the value before the change?". If an item ended up at $68 already with 15% off, what was the original price? The common mistake is to add 15% back — wrong, because the 15% came off the larger value (the original), not the $68.
The key idea
When a value changes, it becomes the original times a factor. To go back, you divide by that factor.
The three cases
- After an X% discount:
original = value ÷ (1 − X/100) - After an X% increase:
original = value ÷ (1 + X/100) - "is X% of the original":
original = value ÷ (X/100)
Step-by-step example
$68 at 15% off:
- Factor: 1 − 0.15 = 0.85
- Original: 68 ÷ 0.85 = $80
Check: 80 with 15% off = 80 × 0.85 = 68. It matches.
Practical use: pre-tax price
Find the value before an embedded tax: a $110 final price with 10% tax came from 110 ÷ 1.10 = $100.
FAQ
Why not add the percentage back? Because it was taken from the larger value. Adding 15% of 68 gives $78.20 — wrong.
Good for checking a sale? Yes: with the sale price and advertised percentage, you can tell if the discount is real.