Reverse Percentage Calculator

Find the original value before a percentage increase, a discount, or VAT was applied. Pick what happened to the number, and see the original value, a forward check, and — for increases and discounts — the common mistake most people make.

How to Use the Reverse Percentage Calculator

  1. Choose what happened to the value: it increased, decreased (a discount), is a percentage of a whole, includes VAT, needs a margin/markup split, or you want to know what percentage change occurred.
  2. Enter the value(s) you know — the final value and the percentage, or the original and final values for the "What % was it?" mode.
  3. Click "Calculate" to see the original value, a forward check that proves the answer, and — for increases and discounts — the mistake most people make.

Features

What a reverse percentage actually solves

A reverse percentage finds the original value when you only know the value after a percentage change. The key insight is that the percentage was applied to the original value, not the final one — so you divide by the multiplier instead of subtracting the percentage. For example, 132 after a 10% increase is not 132 minus 10% (118.80). It's 132 ÷ 1.10 = 120, because 10% of 120 is 12, while 10% of 132 is 13.20 — the base changed.

Removing VAT (the most common real-world use)

Prices shown to consumers in Denmark and Spain already include VAT (moms / IVA), so a business that needs the net price has to work backwards. In Denmark, 1,250 kr. including 25% moms breaks down to 1,000 kr. net plus 250 kr. moms — VAT is actually 20% of the gross price, not 25%, a detail that trips up a lot of people. In Spain, 121 € including 21% IVA is 100 € net plus 21 € IVA.

Margin vs markup

Both describe "percent profit," but on different bases. Markup is profit as a percentage of cost (cost = price ÷ (1 + markup)). Margin is profit as a percentage of the selling price (cost = price × (1 − margin)). A 30% margin and a 30% markup give different costs — this calculator shows both from the same input so you never mix them up.

Limits to check

For related calculations, try the GST / VAT Calculator, Discount Calculator, or Percentage Calculator.

Frequently Asked Questions

How do I calculate a reverse percentage? +
Divide the final value by the multiplier. After a 20% discount you pay 80%, so divide by 0.8. After a 10% increase, divide by 1.1.
Why can't I just subtract the percentage? +
The percentage was taken from the original value, not from the new value. 132 minus 10% gives 118.80, but the correct original value is 120.
How do I remove VAT from a price? +
Divide by 1 plus the VAT rate. With 20% VAT, 600 divided by 1.2 is 500 before VAT.
What's the difference between margin and markup? +
Markup is profit as a percent of cost; margin is profit as a percent of the selling price. A 30% margin equals about a 42.86% markup.
Does the order of several percentage changes matter? +
No. Multiplication is commutative, so a 10% increase followed by a 20% decrease gives the same result as a 20% decrease followed by a 10% increase.
Is this reverse percentage calculator free? +
Yes. It's completely free, with no signup, and every calculation runs in your browser — nothing is uploaded to a server.

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