BIDMAS: GCSE Mathematics Definition

What is BIDMAS?

BIDMAS is an acronym to help you remember the order that arithmetic operations should be carried out in a complicated expression. The letters stand for:

• Brackets: ( )

• Indices (or powers): ², ³, √ and similar, including surds and roots

• Divisions or Multiplications: × or ÷, and including fractions

• Additions or Subtractions: + or -

If you need to work out a complicated expression, start by dealing with the brackets, then go on to the indices (i.e. powers), etc. If there is more than one division and/or multiplication, you can just work them out from left to right. The same for more than one addition and/or subtraction, just work them out from left to right.

Modern calculators will automatically follow the BIDMAS order, so as long as you enter an expression correctly, the calculator will give you the correct answer. Note that extra correctly used brackets will still give a correct answer. But leaving out an essential pair of brackets (for example around a negative number) can lead to an incorrect answer.

What is BODMAS?

Sometimes you will come across references to ‘BODMAS’. This is exactly the same thing as BIDMAS. Only, instead of using an ‘I’ from ‘Indices’, an ‘O’ is used from ‘Order’ or ‘POwers’.

BIDMAS Revision Resources to Ace Your Exams

For a more detailed description of BIDMAS, see our revision notes on Mathematical Operations. You can also have a go at our related exam questions and flashcards to test your understanding. Don’t forget to check out the past papers for more general exam revision.

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