Percentage Calculator — Every Kind, With the Working
Every everyday percentage question on one page, each answered as you type: a percentage of a number, what percent one number is of another, percentage change, adding or taking off a percentage, finding the original price before VAT or a discount, percentage difference, and several changes in a row. Each answer shows the formula with your numbers, so you can check it.
Percentage of a number
What is % of ?
What percent is it?
is what % of ?
Percentage change
From to
Add or take off a percentage
by %
Find the original (reverse %)
is after a %
Percentage difference
Between and
Several changes in a row
Start at then change by %
What Percentage Calculator does
Every question on one page
Most sites give each percentage question its own page. Here all seven sit side by side, so you do not need to know the name of the calculation to find the right one — just read the sentences.
The working, with your numbers
Under every answer is the formula filled in, like (100 − 80) ÷ 80 × 100 = 25%. Check it, copy it into homework, or learn the pattern once and stop needing a calculator.
Reverse percentages done right
£120 including 20% VAT was £100, not £96. The reverse calculator divides by the multiplier instead of taking the percentage off again — the mistake most people and many spreadsheets make.
Changes in a row
Up 10% then down 10% is not back where you started — it is 1% down. Enter a list of changes and see the running value and the true net change.
No floating-point noise
Computers turn 0.1 × 3 into 0.30000000000000004. Every result here is cleaned to 15 significant digits, so you see 0.3.
Type numbers the way you write them
1,250 and 1250 both work, a trailing % is ignored, and 12,5 is read as twelve and a half. A box that cannot be read is outlined instead of silently treated as zero.
How it works
Find your question
Each card is a sentence, like "What is 15% of 80?" — pick the one that matches.
Type your numbers
The answer updates on every keystroke. Clicking a box selects its number, ready to replace.
Check the working
The line under the answer shows the formula with your numbers in it.
Copy the result
Copy puts the plain number on your clipboard, ready for a spreadsheet.
Cheatsheet
The tokens you reach for most, at a glance.
X% of YX ÷ 100 × YX is what % of YX ÷ Y × 100% change(new − old) ÷ |old| × 100Increase Y by X%Y × (1 + X ÷ 100)Decrease Y by X%Y × (1 − X ÷ 100)Original before +X%result ÷ (1 + X ÷ 100)% difference|A − B| ÷ ((A + B) ÷ 2) × 100How people use it
Shopping and discounts
What is 30% off £85? What was the price before the 25% sale? Which of two offers is the bigger saving?
VAT and sales tax
Add 20% VAT to a net price, or strip it out of a gross figure with the reverse calculator.
Pay rises, prices and investments
How big was that rise in percent? What does three years of 4% inflation add up to? Successive changes answers both.
Marks and results
Turn 42 out of 60 into a percentage, or compare two scores fairly with percentage difference.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 15% of 80 is 15 ÷ 100 × 80 = 12. A shortcut: 10% is the number with the decimal point moved one place left, so 15% is that plus half of it again.
How do I work out percentage change?
Subtract the old value from the new one, divide by the old value, and multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. The old value always goes on the bottom, which is why going back from 100 to 80 is only a 20% fall.
How do I find the price before VAT or a discount?
Divide by the multiplier, do not subtract the percentage. A price of 120 including 20% VAT is 120 ÷ 1.20 = 100. A sale price of 75 after 25% off is 75 ÷ 0.75 = 100. Taking 20% off 120 gives 96, which is wrong. Use the Find the original card.
What is the difference between percentage change and percentage difference?
Percentage change has a direction: it measures from an old value to a new one. Percentage difference compares two values with neither as the starting point, dividing by their average, so 40 vs 60 and 60 vs 40 both give 40%. Use change for before-and-after, difference for comparing two things side by side.
Why is +10% then −10% not zero?
Because the second change is a percentage of a different number. 100 up 10% is 110; 10% of 110 is 11, so down 10% lands on 99. Percentage changes multiply rather than add — the Several changes card shows the true net change.
What is a percentage point?
The plain difference between two percentages. An interest rate going from 4% to 5% has risen one percentage point, but by 25% in relative terms. News reports mix the two up often; see percentage points vs percent.
Why can't I calculate a change from zero?
A percentage change divides by the starting value, and dividing by zero has no answer — any increase from nothing is infinitely large in percentage terms. Report the absolute change instead.
Last updated 2026-09-15