Reverse Percentage Calculator
Find the original number before a percentage was added or taken off: the price before tax, before a discount, or the whole from a part.
Working
1,180 ÷ (1 + 18 ÷ 100) = 1,180 ÷ 1.18 = 1,000
Difference between the final and original value: 180.
Reverse percentage formulas
- After an increase: original = final ÷ (1 + P ÷ 100)
- After a decrease: original = final ÷ (1 − P ÷ 100)
- From a part: whole = part × 100 ÷ P
- Don't just subtract the percentage: taking 18% off ₹1,180 gives ₹967.60, not the original ₹1,000.
Reverse Percentage Calculator: frequently asked questions
What is a reverse percentage?
It works backwards from a number that already has a percentage added or taken off, to find the original. For example, finding the price before 18% tax from the price after tax.
How do I find the original price before a percentage increase?
Divide the final value by (1 + percentage ÷ 100). If a price is ₹1,180 after an 18% increase, the original is 1,180 ÷ 1.18 = ₹1,000.
How do I find the original price before a discount?
Divide the sale price by (1 − discount ÷ 100). If an item costs ₹800 after a 20% discount, the original price was 800 ÷ 0.8 = ₹1,000.
Why can't I just subtract the percentage from the final price?
Because the percentage was worked out on the original, not the final value. Taking 18% off ₹1,180 gives ₹967.60, but the original was ₹1,000.