The Problem

You've got a basic calculator, or you're using the calculator app on your phone, and you need to work out VAT on a price right now - no time to look up a formula, just the actual buttons to press. This guide gives you the exact keystrokes, for both adding VAT and removing it, on any ordinary calculator.

Adding VAT: The Button Sequence

To add 20% VAT to a price, using a completely basic calculator with just number keys and +, -, ×, ÷:

  1. Type in your price - for example, 100
  2. Press ×
  3. Type 1.2
  4. Press =

Result: 120. That's your price including VAT.

Multiplying by 1.2 does two things in one step: the "1" keeps your original price, and the ".2" adds 20% on top. It's the same as calculating the VAT separately and adding it on, just faster.

For the 5% reduced rate, use 1.05 instead of 1.2 in step 3. For any other percentage rate, add 1 to the rate as a decimal - a 15% rate becomes 1.15, a 23% rate becomes 1.23.

Removing VAT: The Button Sequence

This is the one that trips people up, because the instinct is to subtract 20% - which gives the wrong answer. To correctly find the price before VAT from a VAT-inclusive total:

  1. Type in the VAT-inclusive price - for example, 120
  2. Press ÷
  3. Type 1.2
  4. Press =

Result: 100. That's the price before VAT.

Why divide instead of subtract? The 20% was originally calculated on the smaller number (100), not the bigger one (120). Subtracting 20% of 120 removes too much - you'd get 96, not 100. Dividing by 1.2 reverses the original calculation exactly, which subtracting can never do.

To then find just the VAT amount on its own, subtract your answer from the original price: 120 - 100 = 20.

Using the Percentage (%) Key

Many calculators, including most phone calculator apps, have a dedicated % key. It can genuinely speed things up, but it behaves differently across different calculators, which causes a lot of confusion.

Adding VAT with the % key

On most calculators with a percentage key, this sequence works: 100 + 20 % =. Type the price, press plus, type the VAT rate as a whole number, press the percent key, then equals. Many calculators will show 120 directly.

Removing VAT with the % key

This is where percentage keys become unreliable. There is no standard "reverse percentage" button on ordinary calculators - the % key is built for adding or taking a percentage off a number you already know, not for working backwards from a VAT-inclusive total. For removing VAT reliably, the division method above (dividing by 1.2) is the method that works consistently on every calculator, every time.

Percentage keys vary more than people expect between calculator brands and phone models - the same button sequence can give different results on different devices. If you want a method that works identically everywhere, the multiply/divide approach above is the reliable one.

On an iPhone or Android Calculator

The standard calculator app on both iPhone and Android supports the same basic +, -, ×, ÷ buttons described above, so the multiply-by-1.2 and divide-by-1.2 methods work exactly the same way. On an iPhone specifically, turning the phone sideways opens a scientific calculator with more functions, though the basic VAT methods above don't require it - the standard portrait view is enough.

Worked Examples

What you have Buttons to press Result
Add 20% VAT to 250250 × 1.2 =300
Remove 20% VAT from 300300 ÷ 1.2 =250
Add 5% VAT to 8080 × 1.05 =84
Remove 5% VAT from 8484 ÷ 1.05 =80

Common Mistakes

  • Subtracting 20% instead of dividing by 1.2. The single most common calculator mistake - always gives an answer that's too low when removing VAT.
  • Using the % key to remove VAT. Percentage keys are built for adding or taking a cut off a known number, not reversing a VAT-inclusive total. Use division instead.
  • Forgetting to press equals. Sounds obvious, but on some calculators the display updates automatically and on others it only shows the correct result after pressing =.
  • Rounding too early. If you're doing several steps, keep the full decimal result until your final answer, then round to two decimal places at the very end.

Skip the Button-Pressing With WaqarWeb

If you'd rather not do the maths by hand at all, the VAT Calculator does exactly this instantly - enter a price, choose add or remove VAT, pick the rate, and it shows the net, VAT and gross figures with no risk of a keystroke mistake.

Frequently Asked Questions

What do I multiply by to add VAT?

1.2 for the UK standard 20% rate. Multiply your price by 1.2 and press equals to get the total including VAT.

What do I divide by to remove VAT?

1.2 for the UK standard 20% rate. Divide your VAT-inclusive price by 1.2 and press equals to get the price before VAT.

Can I use the percentage button to work out VAT?

Yes for adding VAT (a sequence like 100 + 20 % = usually works), but the percentage key is unreliable for removing VAT from a total. Use division for that instead.

Does this work on any calculator, or just certain brands?

The multiply-by-1.2 and divide-by-1.2 methods work identically on any basic calculator, phone calculator app, or scientific calculator, since they only use the standard multiply, divide and equals functions found on every calculator.

How do I work out just the VAT amount, not the total?

Work out the total first using the methods above, then subtract the original price from it. For example, to add VAT to 100: calculate 100 × 1.2 = 120, then 120 - 100 = 20, which is the VAT amount.