Why mental maths is important


use of boards to show thinking

Mental maths is essential because it lays the foundation for more complex maths.

When a child is asked (usually around Year 4) to add numbers using column addition, they'll need to bring several aspects of mental maths into play. To add up the numbers in each column quickly, they'll need to be well-practised at adding single-digit numbers in their heads.

To understand that adding the 3 and the 8 in the 10s column really means adding 30 and 80, they need to have a strong grasp of place value. Children need to understand what is happening to numbers when they calculate, rather than just relying on formulas.

Mental maths takes a lot of practice, and the more you can do with your child at home, the better you'll prepare them for the maths they'll encounter in class and in tests (and in everyday life). Little and often is definitely the key. Some things you may want to practise are:

  • Counting (eg counting in 2s, 5s or 10s)
  • Place value (eg understanding that the 3 in 37 means 30, rather than just 3)
  • Number facts (eg times tables, or pairs of numbers that add up to 10)
  • Simple additions and subtractions (eg 32 + 5)


Children have mental maths every day. This is usually set within practical activities (eg How many fingers? How many sweets are on the plate? Can you count to 5? 10? Can you count backwards from 5? 10? What number comes after 4? 6?).

This helps children to develop their knowledge of how numbers are used in everyday life. If regular practice and repetition take place, children develop confidence in using numbers for counting. The emphasis is (or should be) on the enjoyment and fun of everyday opportunities for counting. 

Key Stage 1 and 2

Mental maths usually takes place for 15–20 minutes every day in school. As with younger children, repetition and practice are essential if they are to become confident and competent.

Key Stage 1

Children count backwards and forwards, use number facts and place value. They add and subtract one-digit or two-digit numbers. They start at a given number and count on in tens, count in odd or even numbers and solve simple problems (eg I have 20 pencils in this box, but there are 23 children in the class. How many more will I need?).

They learn quick recall of number facts to 10 (eg 7 + 0 = 7, 6 + 1 = 7 etc.) They learn the multiples of 10 that total 100 (eg 80 + 20, 90 + 10) and can work out 40 + 24 or 30 + 28.

Children at this stage also learn to 'cross 2'. When working out a sum such as 16 + 7 = 23, they will work out that 16 + 4 = 20 (making the first number up to 20) and then 20 + 3 = 23.

Alternatively, they may use another strategy such as 16 + 10 = 26 and then take away 3 making 23.  

Key stage 2

In KS2, children use a range of mental methods, involving number facts and place value, to add, subtract, multiply and divide numbers to 100 or more. They practise these on a daily basis through oral and mental work.

They learn to give 2 numbers that add up to 20, 50, etc. They will be asked to recall 2, 3, 4, 5 and 10 times tables. They will need instant recall of these to help them with their calculations of higher numbers.

By Year 6, they will be doubling and halving numbers, using effective strategies for multiplying. For example, when multiplying by 15, they may first multiply by 10, halve the result and then add the two together (eg 20 × 15 is the same as 20 × 10 (200) plus 20 × 5 (100), so 200 + 100 = 300).

All this helps to secure speed in mental calculations. Practice, rehearsal and reasoning are essential if children are to become confident and skilful with numbers. 



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Last updated: 29-Jun-2012 at 9:14 AM