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Adult maths guide

How to get faster at mental maths: methods and practice

By Lee Trett, Founder · Published 19 October 2026

To get faster at mental maths, practise choosing a useful method before trying to calculate more quickly. For 58 + 27, add 20 to reach 78, then 2 to reach 80 and the remaining 5 to reach 85. Build accuracy with manageable calculations, then compare your speed on fresh questions of similar difficulty.

What is slowing your mental maths down?

A slow answer can come from different steps: recalling a number fact, choosing a method or keeping an intermediate result in mind. Identify the step that stalls before choosing practice. If you can explain the method but pause at a multiplication fact, work on that fact; if the numbers become muddled, shorten the calculation or write a temporary subtotal.

Try 8 + 7, 46 + 29, 83 − 78 and 6 × 8 without a timer. The answers are 15, 75, 5 and 48. Note where you hesitated. These questions are a starting check, not a test of intelligence or a standard that every adult must meet.

If the first calculation needs careful counting, revisit number bonds. If the facts are familiar but choosing a route is difficult, use the table below. You do not need to learn every method at once.

Which mental maths method should you choose?

Choose a method that makes the particular numbers convenient. Partitioning separates tens and ones; compensation uses a nearby round number and corrects the change; counting up finds a small difference. The useful question is “Which calculation can I already do?” Use that known calculation as a stepping stone to the one in front of you.

For the subtraction, count from 97 to 100, a jump of 3, then from 100 to 103, another jump of 3. The total jump is the difference. You have not subtracted the digits separately.

How do you add and subtract without losing track?

Keep one running total when adding or subtracting mentally. Change it in manageable stages and say the subtotal to yourself before continuing. For 68 + 27, add the 20 first, then the 7. Holding 88 and one remaining step can be more manageable than remembering several separate tens and ones totals.

1. Split 27 into 20 and 7.
2. Calculate 68 + 20 = 88.
3. Bridge through 90: 88 + 2 = 90, then 90 + 5 = 95.

Compensation needs a different check: did your change make the result too large or too small? For 74 − 29, calculate 74 − 30 = 44, then add 1 back to get 45. Subtracting 30 removed one more than intended. For addition, rounding an added number upwards requires subtracting the excess instead.

How do known facts shorten multiplication and division?

Use a multiplication fact you know to construct one you do not. For 7 × 8, start with five lots of 8 and add two lots of 8: 40 + 16 = 56. For division, ask the matching multiplication question. To solve 72 ÷ 8, ask how many eights make 72.

You can also rearrange a product without changing its value. For 16 × 25, halve 16 and double 25 to get 8 × 50 = 400. Halve one factor and double the other together; changing only one changes the answer. This method is useful here because 50 is a convenient multiplier.

For 72 ÷ 8, knowing 8 × 9 = 72 gives 9. Check by multiplying the answer by the divisor. Our mental maths strategies guide gives more examples of building calculations from familiar facts.

Should you practise with a timer?

Practise an unfamiliar method without a timer so you can check each step. When you can use it accurately, timing a short set can help you compare your own attempts. Record the number correct alongside the time, keep the question types comparable and avoid treating a faster but less accurate round as automatic progress.

Use fresh questions for the comparison. Repeating the same list may test whether you remember its answers. Keep conditions similar too: mental-only work and work with written subtotals are different tasks. A timer is optional; fewer restarts and a clearer explanation are useful observations even when you do not record seconds.

What could a short practice session look like?

Choose a small session you can finish attentively: recall a few useful facts, work through one method, then check a mixed set. Five minutes is a suggested starting point, not a promised dose or deadline. If you are getting stuck repeatedly, reduce the number range and work through one example with its answer visible.

• Recall: review the pairs that make 10 or a few multiplication facts you need.
• Apply: solve several questions using one method and explain a step aloud.
• Choose: try a mixed question without a method label.
• Review: correct one error and write the reason it happened.

For example, a note reading “forgot to add one back after subtracting 30” tells you what to revisit. “Bad at subtraction” does not identify a repair.

Can you choose a method for these practice questions?

Try these questions without looking at the answers. Choose a route before calculating and allow a short jotting if you need one. The suggested methods in the answer table are options, not compulsory procedures. If your method is accurate and you can explain it, compare the steps rather than rejecting it because it looks different.

1. 57 + 28
2. 86 + 39
3. 92 − 38
4. 204 − 197
5. 24 × 5
6. 18 × 25
7. 84 ÷ 7
8. 15% of £60

Where can you practise next?

Use the exercise that matches the difficulty you noticed. Return to number facts if recall interrupts every calculation; practise choosing between methods if the arithmetic itself is comfortable. For a change of format, play the adult browser puzzle. Beequation is a mental maths puzzle game by Trett Labs Limited; its adult version is Beequation Pro.

What should you learn next?

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