Addition and subtraction are the foundation of all mental math. Get quick at these and everything else — multiplication, estimation, making change — becomes easier. These are the core methods, in the order most people find natural to learn them.
Our number system is built on tens, so the fastest adders constantly build tens along the way. To add 8 + 5, notice that 8 needs 2 to reach 10. Take that 2 from the 5, giving 10 + 3 = 13. With bigger numbers the idea scales: 47 + 6 → 47 needs 3 to reach 50, so 50 + 3 = 53. You're never really adding awkward digits — you're always stepping to the next ten.
For two-digit sums, add the tens first, then the ones. 36 + 47: 30 + 40 = 70, then 6 + 7 = 13, then 70 + 13 = 83. Saying the big part first means you always have a sense of the answer's size, which prevents wild mistakes.
When a number is close to a round one, round it, do the easy sum, then correct. 58 + 27: round 58 up to 60 (27 + 60 = 87), then subtract the 2 you borrowed: 85. For subtraction, 74 − 38: round 38 up to 40 (74 − 40 = 34), then add the 2 back: 36. The trick is remembering which way to adjust — if you rounded up what you're adding, you subtract back; if you rounded up what you're taking away, you add back.
Subtraction feels harder than addition because "borrowing" is clumsy in your head. The fix: don't take away — count up. For 52 − 37, start at 37 and climb: 37 → 40 is 3, 40 → 52 is 12, so the answer is 3 + 12 = 15. This is exactly how a cashier counts change, and it avoids borrowing entirely.
Split a tricky number into friendly chunks. 63 − 28 can be done as 63 − 20 − 8 = 43 − 8 = 35. You take away the tens first, then the ones, so you only ever deal with small steps.
When you have several numbers to add, scan for pairs that make tens or hundreds and group them first. In 6 + 4 + 7 + 3, pair 6 + 4 = 10 and 7 + 3 = 10, giving 20 at a glance. Grouping is far faster than adding strictly left to right.
These methods only get fast when a tiny bit of time pressure stops you from falling back on slow digit-counting. That's the whole idea behind a round-based game: each prompt is a rep, and the timer nudges you toward the shortcut. Try a few rounds of MathLeap, then read the times tables guide to carry these habits into multiplication. More in our guides.