Free · no registration · works on your phone
Percentage calculator – work out percentages fast
Work out a percentage share, a discount, an increase, a percentage change and a reverse percentage. You see both the answer and the formula it came from straight away – so you can check the sum yourself.
- 5 calculation modes
- Formula shown
- Comma and point both work
- History in your browser
Your recent calculations
Calculations are saved only in this browser (localStorage). They are not sent to the server and we cannot see them.
What can this percentage calculator work out?
A percentage calculation is always the same thing asked from different angles: part, whole and percentage. When you know two of them, the third follows. The calculator's five tabs cover all the usual questions, so you don't have to remember whether the division went one way or the other.
| Mode | Question | Inputs | Formula |
|---|---|---|---|
| Percentage of a number | How much is 25% of 80? | Percentage, number | number × p / 100 |
| What percentage | What percentage is 18 of 72? | Part, total | a / b × 100 |
| From what number | 45 is 15% of what number? | Part, percentage | a / (p / 100) |
| Add or subtract | How much is £1,250 + 12%? | Value, change %, direction | value × (1 ± p/100) |
| Percentage change | What is 240 → 312 as a percentage? | Old and new value | (new − old) / old × 100 |
Each result also shows the rows people usually ask for next: how much is left, what the multiplier is, what the opposite-direction percentage is, and how much the same sum comes to ten times over. So you don't have to run the calculation again with new numbers.
How to use the percentage calculator
1. Choose a calculation
The buttons along the top switch between calculations. If you're not sure which one you need, think about which number is the "whole thing", i.e. 100%, in your case. In a discount it's the normal price, in a survey it's the total number of respondents, and in a pay rise it's the old salary.
2. Type the numbers
You can write 12.5 or 12,5 – either works. Spaces or commas used as thousands separators
(1,250), the pound sign and the per cent sign are cleaned up automatically, so you can paste a figure
straight from an online shop or an invoice.
3. Read the result and check the formula
The result appears as you type. The receipt-style result card shows the big answer, a plain-English explanation ("25% of 80 is 20"), the full formula with the numbers filled in, and extra rows. You can copy the formula with a button, for example into an email or your notes.
4. Share or save
Share calculation creates a link with the numbers you entered included – the recipient sees the same calculation ready to go. Your most recent calculations also stay visible below the calculator, so when you come back to the page you can see what you worked out last. The data stays in your own browser.
The percentage calculator in everyday situations
The same calculation gets a different name depending on where it's used. Below are dedicated calculators for the most common situations – there the field names, examples and extra details are written for that exact situation.
Percentage formulas and examples
There are really only four formulas. Everything else is a combination of them.
Percentage of a number
part = number × percentage / 100
Example: a shop offer says "−30%". The item costs £59. The discount in pounds is
59 × 30 / 100 = £17.70, so you pay £41.30.
Share as a percentage
percentage = part / whole × 100
Example: 43 out of 250 customers answered the survey. The response rate is
43 / 250 × 100 = 17.2%.
The whole, backwards
whole = part / (percentage / 100)
Example: a deposit of £4,500 is 15% of the purchase price. The purchase price is
4,500 / 0.15 = £30,000.
Percentage change
change % = (new − old) / old × 100
Example: an electricity bill rose from £78 to £96. The increase is
(96 − 78) / 78 × 100 = 23.08%. Note that the reference number is the old value.
If you calculated it the other way round, you'd get a different percentage.
A fuller collection of formulas, rules of thumb and practice exercises is on the percentage formulas page. If you want to learn to work out percentages in your head, read the guide on calculating discounts and increases.
Supported input formats and rounding
| You type | The calculator reads | Note |
|---|---|---|
12.5 | 12.5 | Decimal point |
12,5 | 12.5 | A comma works just as well |
1,250 or 1250 | 1,250 | Comma as a thousands separator |
£79.90 | 79.9 | The pound sign is removed |
25% | 25 | The per cent sign is removed |
-15 | −15 | Negative numbers allowed |
Results are shown by default to two decimal places, and whole numbers without unnecessary zeros. For sums of money, rounding is to the nearest penny. If you need a calculation for your accounts or an invoice, always check the final figure in your own system as well – rounding rules can differ from line to line.
What the calculator's figures are based on
Percentage calculation itself is maths that doesn't change over the years: the formulas are the same as in a school textbook. The percentages linked to the calculators, however – VAT rates, National Insurance and pension contributions, and trade union subscriptions – change regularly.
- VAT rates are based on HMRC's current rates. The rates and their effective dates are given on the VAT calculator page.
- National Insurance and pension contributions are confirmed each tax year. We use the latest confirmed employee rates as defaults, but you can change them yourself.
- Your Income Tax rate is always personal to you. We don't guess it for you – you enter your own rate, which you can find on your payslip or in your HMRC account.
The calculators give a mathematical result from the numbers you enter. They are not a tax assessment, a credit decision, health advice or an official payslip. For official matters always use the relevant authority's own service.
The basics of percentage calculation
Per cent means a hundredth, so a percentage works as a multiplier. Below are the formulas the calculator uses, the key concepts, and what the calculator does not answer.
Formulas and examples
Percentage of a number
result = number × percentage / 100Example
An offer of −30% off a price of £59: 59 × 30 / 100 = £17.70 discount.
Note
The result is the part, not the amount left over. What's left is £41.30.
Share as a percentage
percentage = part / whole × 100Example
43 respondents out of 250: 43 / 250 × 100 = 17.2%.
Note
The divisor is the number that is 100% in the task.
The whole, backwards
whole = part / (percentage / 100)Example
A deposit of £4,500 is 15%: 4,500 / 0.15 = £30,000.
Note
The answer must be larger than the starting number. If it isn't, the direction of calculation is wrong.
Percentage change
change % = (new − old) / old × 100Example
An electricity bill £78 → £96: 18 / 78 × 100 = 23.08%.
Note
The reference number is always the old value. Calculated the other way round the percentage is different.
Concepts and classification
| Per cent | A hundredth. 25% = 0.25 = a quarter. |
|---|---|
| Percentage point | The difference between two percentages. 2% → 3% = 1 percentage point. |
| Per mille | A thousandth. 1% = 10‰. |
| Reference value | The number that is 100% in the calculation. It changes with the task. |
| Multiplier | A percentage as a decimal. +12% = multiplier 1.12, −12% = 0.88. |
Limitations of the calculator
- A percentage change cannot be calculated if the original value is zero.
- The calculator rounds the displayed result; the calculation is done at full precision.
- The calculator does not know what units the numbers represent – interpretation is up to you.
- Successive percentage changes are not added together but multiplied.
How up to date the information is
When it was checked
Content and the percentages used were checked on 12 August 2026.
Disclaimer
The calculator gives a mathematical result from the numbers you enter. It is not an official decision, an offer or professional advice. See the terms of use.
Topics
This calculator belongs to the following topic areas. On the topic page you'll find all the calculators and guides on the same theme in one place.
All calculators
Every calculator is built for one precise need – the field names and examples are written in the language of that situation.
What users say
★★★★★
I use this in the shop almost every week. The best bit is seeing the saving in pounds straight away, not just the final price.
★★★★★
I teach maths and use the formula display in class. The students can see where the number comes from.
★★★★☆
The VAT section is clear. I'd still like ready-made templates for the calculation rows, but otherwise it works well on the phone.
Feedback is collected through the site's feedback form and published with a first name only. We don't show a star average in search results, because we don't collect verified reviews.
Frequently asked questions about the percentage calculator
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100: a / b × 100. For example, 18 of 72 is 18 / 72 × 100 = 25%. Choose the What percentage? tab and enter the part and the total.
How do I find the whole when I know a part and its percentage?
This is a reverse percentage: part / (percentage / 100). If 45 is 15% of some number, the whole is 45 / 0.15 = 300. Use the From what number? tab.
Is the percentage calculator free and do I need to register?
The calculator is completely free and needs no registration, account or app download. It runs in the browser on both computer and phone. You can also add the page to your phone's home screen so it opens like an app.
Can I type a decimal comma or do I need a point?
Both work. The calculator recognises both 12.5 and 12,5. Spaces or commas used as thousands separators, the pound sign and the per cent sign are cleaned up automatically, so you can paste a figure straight from an online shop.
What is the difference between a per cent and a percentage point?
A percentage point is the difference between two percentages. If an interest rate rises from 2% to 3%, the rise is 1 percentage point but 50 per cent. The difference is large for things like interest rates, tax rates and research results. You can work out both with the percentage change calculator.
Why don't a price rise and a fall cancel each other out?
Because the reference number changes. If £100 rises 20%, the price is £120. When £120 falls 20%, the result is £96 – not £100. In the second calculation the 20% is taken from a larger number. The calculator always tells you which number is the reference value.
Is this the same as some other percentage calculator I've used before?
No. This is an independent site and we are not connected to any other service. If you're looking for a specific site, it's best to search for it by its own address. If you just want a working percentage calculator, you can use this one – the methods are the same, because the maths is the same.
Are my calculations saved anywhere?
Your most recent calculations are saved only in your own browser (localStorage) to make it easier to return to the page. They are not sent to the server and we cannot see them. You can clear the history at any time with the button below the calculator.