The most useful mental math tricks for kids are simple strategies: doubles, near doubles, making 10, adding 9 as "add 10, take 1," rounding and adjusting, splitting into tens and ones, and counting up to subtract. Each makes a hard problem easier. Teach one at a time and ask your child to explain it.
Mental math isn't about memorizing a bag of tricks. It's about seeing that numbers can be broken apart and put back together in friendlier ways. The Common Core standards build this in from first grade, listing strategies such as counting on, making ten, using the link between addition and subtraction, and "creating equivalent but easier or known sums." By second grade, children are asked to explain why their addition and subtraction strategies work, using place value. By third grade, they are expected to add and subtract within 1000 fluently using strategies and algorithms.
So the goal is understanding first and speed later. A child who knows why a trick works can rebuild it when memory fails.
The ages are rough guides. Start with whatever fits your child.
Doubles are facts like 3 + 3, 6 + 6 and 7 + 7. They are easy to picture: an egg carton holds 6 + 6, and two hands show 5 + 5. Once doubles are solid, many other facts become easy.
Practice: roll one die and double it, or call out a number and have your child shout its double.
When two numbers are one apart, use the double you know. The first grade standards give this example: 6 + 7 = 6 + 6 + 1 = 12 + 1 = 13.
8 + 7: double 7 is 14, plus 1 is 15.
8 + 9: double 8 is 16, plus 1 is 17.
Fill up a ten first. The standards' example: 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14. England's NCETM calls this bridging 10.
9 + 5: 9 needs 1. Split 5 into 1 and 4. 10 + 4 = 14.
7 + 6: 7 needs 3. Split 6 into 3 and 3. 10 + 3 = 13.
This one depends on knowing the pairs that make 10. Our number bonds to 10 guide covers them.
Adding 10 is easy, so add 10 and then take 1 away.
7 + 9: 7 + 10 = 17, then 17 - 1 = 16.
46 + 9: 46 + 10 = 56, then 56 - 1 = 55.
46 + 19: 46 + 20 = 66, then 66 - 1 = 65.
Subtracting 9 works the other way: 52 - 9 is 52 - 10 = 42, then 42 + 1 = 43.
Round one number to a friendly ten, do the easy sum, then fix the difference.
38 + 25: 40 + 25 = 65. You added 2 too many, so 65 - 2 = 63.
62 - 28: 62 - 30 = 32. You took away 2 too many, so 32 + 2 = 34.
A neat variation is "give and take." For 38 + 25, move 2 from the 25 to the 38: 40 + 23 = 63. The total doesn't change, but the sum is easier.
Break both numbers into tens and ones, add the parts, then combine. The first grade standards describe adding two-digit numbers by adding tens and tens, ones and ones, and sometimes making a new ten.
34 + 25: 30 + 20 = 50, 4 + 5 = 9, so 59.
47 + 36: 40 + 30 = 70, 7 + 6 = 13, and 70 + 13 = 83.
Another version keeps the first number whole: 47 + 36 is 47 + 30 = 77, then 77 + 6 = 83.
First graders are expected to find 10 more or 10 less than a two-digit number in their heads, without counting. Second graders add or subtract 10 or 100 mentally for numbers from 100 to 900.
54 + 10 = 64, and 54 + 30 = 84.
372 + 100 = 472, and 372 - 10 = 362.
Subtraction is the distance between two numbers. The first grade standards point out that knowing 8 + 4 = 12 means you also know 12 - 8 = 4. For numbers that are close together, count up:
52 - 47: from 47, 3 more makes 50, and 2 more makes 52. 3 + 2 = 5.
13 - 9: from 9, 1 more makes 10, and 3 more makes 13. The answer is 4.
Numbers one apart: near doubles.
A number ending in 8 or 9: make 10, or round and adjust.
Two two-digit numbers: split into tens and ones.
Subtracting numbers that are close: count up.
Adding a multiple of 10: jump by tens.
Ask for the how. After any answer, ask, "How did you work that out?" Then, "Could you do it another way?"
One trick a week. Name it, show it with objects or a drawing, then use it in everyday moments.
Use real life. "We have 38 stickers and get 25 more. How many now?"
Share your own thinking. Say how you would solve it, so your child hears that there's more than one route.
Accuracy before speed. Add a gentle time challenge only once a strategy feels comfortable.
Card and dice games are an easy way to get lots of practice. See our guide to math practice at home for kids for more.
Pick the strategy that fits the numbers. Adding 9 or 19? Add 10 or 20 and take 1 away. Two-digit numbers? Split into tens and ones.
Compensation means changing a number to make the problem easier, then adjusting the answer. For 38 + 25, add 40 + 25 = 65, then take away the extra 2 to get 63.
Under the Common Core, first graders use strategies like making ten and near doubles within 20 and find 10 more or less mentally. Second graders add and subtract within 100 using place value strategies, and third graders work within 1000.
Both matter. The standards ask children to connect strategies to written methods. Mental math is also handy for checking whether a written answer makes sense.
Number Beasts: Bond Lab turns one of these tricks, making 10, into a puzzle game: you launch a number at a beast, a sum of exactly 10 pops it, and a short shot makes the beast grow so it needs a smaller number next time. A new Daily Lab puzzle is generated on the device each day and can be played offline. It's free, with no ads, accounts, tracking or in-app purchases.
Get Number Beasts free on the App Store
Common Core State Standards: Grade 1, Operations and Algebraic Thinking, standard 1.OA.C.6
Common Core State Standards: Grade 1, Number and Operations in Base Ten
Common Core State Standards: Grade 2, Number and Operations in Base Ten
Common Core State Standards: Grade 3, Number and Operations in Base Ten
Addition and subtraction: bridging 10 (NCETM primary mastery materials)