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Understanding the BIDMAS rule

This guide to the BIDMAS rule is packed with practical examples, teaching strategies and ready-to-use BIDMAS resources to help students master this fundamental mathematical concept.

Author: Teachit's editorial team
Published: 16/04/2025

The BIDMAS rule is a fundamental mathematical concept that helps students solve equations in the correct order. As maths teachers, it's essential that we help our students grasp this concept early to build their confidence in tackling more complex mathematical problems.

Contents

BIDMAS rule mnemonic

What is the BIDMAS rule?

BIDMAS (or BODMAS) is an acronym that is used to remember the correct order of operations. It stands for:

  • Brackets
  • Indices (powers or square roots)
  • Division
  • Multiplication
  • Addition
  • Subtraction

What's the difference between BODMAS and BIDMAS?

BODMAS and BIDMAS are essentially the same rule. The only difference is:

  • BIDMAS uses 'I' for Indices
  • BODMAS uses 'O' for Orders (another term for indices)

Both terms are correct, but BIDMAS is more commonly used in UK schools as 'indices' is the term students will encounter in their textbooks and exams.

How to use BIDMAS

When solving mathematical expressions, students should follow these steps:

  1. First, solve anything inside brackets ()
  2. Next, calculate any indices (powers like squared or cubed numbers)
  3. Then perform division and multiplication (from left to right)
  4. Finally, complete addition and subtraction (from left to right)

Let's look at some examples to demonstrate the BIDMAS rule, from simple to more complex problems:

BIDMAS rule example

BIDMAS examples

Example 1: 4 + 2 × 3

  • First, check for brackets (none present)
  • Check for indices (none present)
  • Multiplication comes before addition
  • So: 2 × 3 = 6, then 4 + 6 = 10
  • Answer: 10

Example 2: (4 + 2) × 3² - 5

  • First, solve brackets: (4 + 2) = 6
  • Next, calculate indices: 3² = 9
  • Then multiply: 6 × 9 = 54
  • Finally, subtract: 54 - 5 = 49
  • Answer: 49

Example 3: 2³ × (15 ÷ 3 + 2) - 4²

  • First, calculate indices: 2³ = 8 and 4² = 16
  • Next, solve brackets: 15 ÷ 3 = 5, then 5 + 2 = 7
  • Then multiply: 8 × 7 = 56
  • Finally, subtract: 56 - 16 = 40
  • Answer: 40

Why is it important to teach BIDMAS?

Teaching BIDMAS is crucial because:

  • It provides a clear structure for solving mathematical problems
  • It ensures consistency in mathematical calculations
  • It prepares students for more advanced mathematics
  • It helps prevent common calculation errors
  • It's essential for GCSE maths and beyond

How to teach BIDMAS

There are lots of different ways to teach BIDMAS to students. Here are our top tips:

1. Start with simple BIDMAS examples

Begin with straightforward calculations that only use two operations, then gradually increase complexity.

2. Use visual aids

Create posters or diagrams that show the order of operations. Colour-coding different operations can be particularly effective.

3. Make it memorable

Use mnemonics or stories to help students remember the order of operations. For example: "Brackets Invite Dogs, Mice And Snakes". It can be fun to encourage students to make up their mnemonics or stories.

4. Practice regularly

Incorporate BIDMAS questions into starter activities and homework assignments. Regular practice helps reinforce the concept. Quick quizzes or puzzles are an engaging way to do this.

5. Common mistakes to address

Watch out for these typical errors:

  • Students performing operations from left to right without following BIDMAS
  • Forgetting to complete all operations within brackets first
  • Confusion between multiplication/division order and addition/subtraction order

Remember to emphasise that division and multiplication have equal priority (work left to right), as do addition and subtraction. This is often a source of confusion for students.

BIDMAS teaching resources

Use these step-by-step guides and practice activities to introduce or review the BIDMAS/BODMAS rule with students:

These quick starter quizzes and puzzles provide regular practice opportunities to strengthen students' understanding of the BIDMAS/BODMAS rule:

Make BIDMAS practice fun with these challenges and games, from BIDMAS codebreakers to dice games:

Browse the full collection of BIDMAS (order of operations) resources.

Teachit's editorial team

The editorial team at Teachit consists of experienced teachers and subject specialists who curate, write, edit and check our content to ensure it is useful, insightful and of the highest quality.

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