10 Mental Math Tricks Every Kid Should Know — With Worked Examples
Mental maths is not about being fast. It is about seeing numbers flexibly: breaking them apart, rounding them, and putting them back together. These ten strategies, ordered by age, give children that flexibility, and each comes with a worked example you can try at the dinner table tonight.
- Why mental maths matters
- Two foundations to check first
- The 10 tricks, with examples
- Which trick at which age
- How to practise without worksheets
- Mistakes that make mental maths harder
Why mental maths matters
A child who can calculate in their head understands how numbers are built. That understanding, often called number sense, is what lets them notice that 198 + 56 must be "a bit more than 250", catch their own mistakes in written calculations, and later handle fractions, percentages and algebra without fear. Mental strategies also free working memory: if 8 + 7 is automatic, the brain has room to think about the actual problem.
Speed comes naturally once strategies are understood. Pushing for speed first usually produces guessing and stress.
Two foundations to check first
Nearly every trick below relies on two things. Spend a week on them if they are not yet solid.
- Number bonds to 10 (and later to 100): 1 + 9, 2 + 8, 3 + 7, 4 + 6, 5 + 5. Your child should know instantly that 7 needs 3 to make 10, and that 64 needs 36 to make 100.
- Doubles and halves: double 6 is 12, half of 18 is 9, double 35 is 70.
The 10 tricks, with examples
1. Make ten (ages 6–8)
To add across ten, first complete the ten. 8 + 5: 8 needs 2 to make 10, so split 5 into 2 and 3. 8 + 2 = 10, then 10 + 3 = 13.
2. Near doubles (ages 6–8)
If two numbers are neighbours, use the double. 6 + 7 = 6 + 6 + 1 = 13. 15 + 16 = 30 + 1 = 31.
3. Add 9 by adding 10 (ages 7–9)
Adding 10 is easy, so add 10 and take one away. 27 + 9 = 37 − 1 = 36. The same idea works for 19, 29 and 99.
4. Split by place value (ages 7–10)
Add tens with tens and ones with ones. 46 + 37: 40 + 30 = 70, 6 + 7 = 13, and 70 + 13 = 83. Children can see this clearly with coins of 10 and 1.
5. Count up to subtract (ages 8–10)
Like a shopkeeper giving change, jump from the smaller number to the larger one. 63 − 48: from 48 to 50 is 2, to 60 is 10 more, to 63 is 3 more. 2 + 10 + 3 = 15. This avoids "borrowing" altogether.
6. Round and adjust (ages 9–12)
Change one number into a friendly one, then correct. 198 + 56 = 200 + 56 − 2 = 254. £4.99 × 3 = £15 − 3p = £14.97.
7. Multiply by 5 (ages 9–12)
Multiplying by 5 is multiplying by 10 and halving. 5 × 46 = 460 ÷ 2 = 230.
8. Multiply a two-digit number by 11 (ages 10–12)
Write the two digits apart and put their sum in the middle. 11 × 36: 3 and 6, 3 + 6 = 9, so 396. If the sum is 10 or more, carry one: 11 × 58: 5 + 8 = 13, so 5 becomes 6, giving 638. Ask your child to check why it works: 11 × 36 = 360 + 36.
9. Double and halve (ages 10–12)
Halving one factor and doubling the other keeps the product the same. 16 × 25 = 8 × 50 = 4 × 100 = 400.
10. Use a friendly neighbour (ages 10–12)
Multiply by a round number, then remove the extra group. 7 × 19 = 7 × 20 − 7 = 140 − 7 = 133. For percentages, use 10% as the friendly number: 15% of 80 is 10% (8) plus 5% (4), which is 12.
Which trick at which age
| Age | Focus | Tricks |
|---|---|---|
| 6–8 | Adding within 20 | Make ten, near doubles |
| 7–9 | Adding two-digit numbers | Add 9 via 10, split by place value |
| 8–10 | Subtraction without borrowing | Count up, round and adjust |
| 10–12 | Multiplication and percentages | ×5, ×11, double and halve, friendly neighbour |
These ages are only a guide. A child is ready for the next trick when the previous one feels easy, not when the calendar says so.
How to practise without worksheets
The best mental maths practice is short, spoken and social.
- One question at dinner. Ask "What is 46 + 37?", then the most important question: "How did you do it?" Let everyone explain their method. Hearing several strategies teaches more than one correct answer.
- Shopping maths. Ask your child to round prices and estimate the total before you reach the till.
- Number plates and house numbers. Add the digits, find the partner to 100, or double the number.
- Estimate first. Before calculating, ask "About how much will it be?" Estimation is the habit that catches mistakes.
Mistakes that make mental maths harder
- Teaching tricks as magic. If a child cannot say why a trick works, they will misuse it. Always show it first with objects, coins or a number line.
- Insisting on one method. Mental maths is about choosing the best path for each calculation. 63 − 48 and 63 − 4 call for different strategies.
- Racing too early. Timers are fun only for children who are already accurate.
- Writing everything down. Paper is useful for recording, but the practice itself should happen in the head and out loud.
Free tools on Kids Learning Hub
Practise these strategies with the Math Race game, the Quick Count game for younger children, and our printable missing-number and word-problem worksheets, which encourage children to think before they calculate. The homepage also has a free daily challenge with five new questions every day.
Short daily mental-maths sessions that adapt to your child’s level — offline and free.
Pick one trick this week, practise it in two-minute bursts, and ask "How did you do it?" every time. Confidence with numbers grows one small strategy at a time.
Frequently asked questions
At what age should children start mental maths?
Simple mental maths can start around age 5 or 6 with counting on and number bonds to 10. Strategies such as splitting by place value suit ages 7 to 9, and tricks for multiplication and percentages suit ages 10 to 12.
How can I help my child get faster at mental maths?
Make sure the foundations, number bonds to 10 and 100 and doubles, are automatic, then practise one strategy at a time for a few minutes a day. Speed follows understanding; timers should come last.
Should children use their fingers for maths?
Fingers are a helpful tool for young children learning to count. If a child still needs fingers for simple additions after about age 8, practise number bonds to 10 so that the facts become automatic.