Reverse Percentage Calculator

Written byOleh Soloninupdated 5 October 2026

Known percentage, %

Which equals

Result

The whole (100%)2,400
Formula360 × 100 ÷ 15
The rest2,040
The rest, %85%

Amount × 100 ÷ percent

Given a percentage and what it amounts to, recovers the whole, and shows how much sits in the remaining share.

It reads backwards but comes up constantly: the sale price is known and the original is not; a report gives a share and its value but never the total; tax was withheld and the gross has to be recovered.

The mechanics simply invert. If 15 percent equals 360, then one percent is 24 and the whole is 2,400.

How to use

Enter the percentage that the known figure represents.
Enter the figure itself — the part you already have.
Read the whole, the remainder and the formula behind the answer.

Knowing the part and needing the whole

This is the ordinary percentage question turned around: 360 is known to be 15% of something. The whole comes from a division — 360 ÷ 0.15 = 2,400, or equivalently 360 × 100 ÷ 15. Adding the percentage back on does not work here; the operation has to be division.

The same formula answers questions about tax and discounts. If a price is 800 after 20% off, the original was 800 ÷ 0.8 = 1,000. If a total of 1,220 includes tax at 22%, the pre-tax figure is 1,220 ÷ 1.22 = 1,000.

Worked out with this calculator. A share above a hundred percent means the known figure exceeds the whole.
Known part	Its share	Whole	Remainder
360	15%	2,400	2,040
800	80%	1,000	200
1,220	122%	1,000	−220
50	0.5%	10,000	9,950
120	120%	100	−20

What this calculator shows

The whole number and the formula that recovered it
What the remaining share is worth, in units and as a percentage
A figure you can verify by running it forward on the sibling page

What to keep in mind

The percentage cannot be zero — nothing can be recovered from a zero share.
To undo a discount, enter the share that survived: after 20 percent off you know 80 percent of the price, not 20.

FAQs

How do I recover the pre-discount price?

Enter the share left after the discount. At 25 percent off, the 75 percent you paid divided by 0.75 gives the original.

How do I get gross pay from net pay?

At a flat 13 percent, net is 87 percent of gross — enter 87 and the amount. Above the progressive threshold the net salary calculator is more accurate.

How do I strip VAT out of a gross figure?

The gross is 120 percent of the net at a 20 percent rate. Enter 120 and the total. The VAT calculator does the same with a breakdown.

Why can't I just add the same percentage back?

The base has changed. Take 20 percent off 1,000 and you get 800; add 20 percent to 800 and you get 960. The inverse of a percentage cut is division, not addition.

360 is 15% of what number?

Of 2,400. The route is division: 360 ÷ 0.15, or 360 × 100 ÷ 15. The remainder to the whole is 2,040, which is the other 85%.

How do I find the price before a discount?

Divide the discounted price by the discount multiplier. After 20% off the multiplier is 0.8, so a price of 800 came from 1,000. Adding 20% back to 800 gives 960 and is the wrong operation.

Worked example

Price before the discount

Input: 80% equals 800

Output: The whole is 1,000

Note: Entering 80 rather than 20 is the crux. A 20 percent discount means the 800 you paid is the remaining 80 percent.

Useful links

All tools in Math & Statistics

Reverse Percentage Calculator

Result

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Useful links