Mental Subtraction Tricks: How to Subtract Fast in Your Head
The fastest mental subtraction tricks skip paper-style borrowing. Try counting up from the smaller number to find the difference, bridging through the nearest 10 as a stepping stone, or rounding what you subtract to something easy and adjusting back. For 64 − 19, subtract 20 to get 44, then add 1 back: 45. Pick the trick that fits.
Why Subtraction Feels Harder Than Addition
You hand over a fifty at the checkout and someone says “your change is $16.24.” Your brain stalls — not because you’re bad at math, but because the school method doesn’t travel well from paper to your head.
Paper subtraction works by borrowing: column by column, right to left, carrying digits as needed. On paper that’s fine. In your head you have to track which columns you borrowed from while holding intermediate results. One distraction and the chain breaks.
Mental arithmetic uses different moves: count ahead, step through a round number, or round and correct. “I freeze when I have to borrow” is a complaint that surfaces constantly in mental math communities. “Counting up clicked for me when making change” comes up just as often. The method switch is what makes the difference.
New to mental arithmetic in general? How to improve your mental math covers the full foundation.
Trick 1 — Count Up to Find the Difference
This one feels counterintuitive the first time: to subtract, you add.
Instead of subtracting down from the bigger number, you count up from the smaller one. The total distance you travel is the answer. Cashiers do this instinctively when making change — “that’s $7.00, so from $7.00 to $10.00 is $3.00” — because thinking “what do I add to reach the target?” is often easier than thinking “what’s left after I take away?”
Worked example: 23 − 7
Start at 7. Add 3 to reach 10. Add 13 more to reach 23. Total added: 3 + 13 = 16.
Worked example: 64 − 58
Start at 58. Add 2 to reach 60. Add 4 more to reach 64. Total added: 2 + 4 = 6.
Notice how clean the second example is. When two numbers are close together, counting up is almost effortless — you barely have to think. Trying to borrow across 64 − 58 on paper takes longer than arriving at 6 by counting up in one breath.
As Math Is Fun’s mental arithmetic guide puts it: “begin with the smaller value and mentally skip your way up the difference, with jumping points at recognizable boundaries, such as powers of 10.” That’s counting up — just described from a mathematician’s angle.
When to use it: The two numbers are close together, or the situation naturally calls for “how much more?” — change, short distances, time differences.
Trick 2 — Bridge Through 10 (The Making-10 Move)
This is the heart of mental subtraction, and it connects directly to one of the oldest number tricks there is.
The idea: instead of subtracting in one jump, use the nearest 10 (or multiple of 10) as a stepping stone. Break the number you’re subtracting into two pieces — the first piece gets you down to 10, and the second piece finishes the job.
Worked example: 16 − 9
Split 9 into 6 + 3.
- 16 − 6 = 10
- 10 − 3 = 7
Worked example: 15 − 7
Split 7 into 5 + 2.
- 15 − 5 = 10
- 10 − 2 = 8
The key skill underneath this trick: being able to see instantly that 7 and 3 make 10, or that 6 and 4 make 10. Once that reflex is sharp, the bridge move happens almost automatically. You recognize the pieces before you’ve consciously decided to use them.
Split what you’re subtracting into two parts: first part gets you to 10, second part finishes. 16 − 9 becomes 16 → 10 → 7.
Just for fun — not medical advice.That “seeing which numbers make 10” reflex is exactly what Make 10 practices — you’re looking for tiles that add up to ten, which is the same instinct you’re building here. If the bridge trick feels slow at first, a few rounds of Make 10 is a low-pressure way to sharpen that particular reflex. No sign-up needed.
When to use it: Subtracting single digits from teen numbers, or whenever the number you’re starting from is just above a multiple of 10.
Trick 3 — Subtract Left to Right (No Borrowing)
Paper subtraction works right to left — ones column first, tens column second — because you need to know if you’re borrowing before you can commit to an answer. Mental arithmetic doesn’t have that constraint. You can start with the biggest piece and work your way down.
Worked example: 58 − 23
- 58 − 20 = 38
- 38 − 3 = 35
Worked example: 76 − 41
- 76 − 40 = 36
- 36 − 1 = 35
You handle the tens first, then peel off the ones. There’s nothing to borrow, no column to track. You hold one intermediate number in your head (38, then 3 to go) instead of a whole column alignment.
This works cleanly when the ones digit of the number you’re subtracting is smaller than the ones digit you’re subtracting from. In 58 − 23, the ones digits are 8 and 3: no crossing needed. When there would be borrowing (say, 52 − 27, where 7 > 2), Trick 4 handles it more cleanly.
When to use it: Multi-digit subtraction where the ones digits don’t require borrowing — bills, measurements, dates.
Trick 4 — Round and Adjust (Compensation)
This is the go-to move whenever the number you’re subtracting is close to a round number — especially when it ends in 8 or 9, or for numbers like 38, 49, or 99.
The move: round up to the nearest clean number, subtract that instead, then add back the difference.
Worked example: 64 − 19
19 is close to 20.
- 64 − 20 = 44
- You subtracted 1 too many, so add 1 back: 44 + 1 = 45
Worked example: 81 − 38
38 is close to 40.
- 81 − 40 = 41
- You subtracted 2 too many, so add 2 back: 41 + 2 = 43
Worked example: 152 − 99
99 is close to 100.
- 152 − 100 = 52
- You subtracted 1 too many, so add 1 back: 52 + 1 = 53
The adjustment is always in the direction that corrects the overshoot: you rounded up (subtracted more than needed), so you add the excess back.
This is the same round-up logic that makes “$7.99” feel like less than $8.00 — the same move how to improve your mental math covers in a shopping context. No need to re-explain it here; the subtraction application is just the flip side of that same reflex.
| Situation | Best trick |
|---|---|
| Two numbers close together, or “how much more?” | Count up |
| Subtracting from just above a round 10 | Bridge through 10 |
| Multi-digit, ones digit doesn’t need borrowing | Left to right |
| Number you’re subtracting ends in 8, 9, or close to round | Round and adjust |
As K5 Learning’s guide to mental subtraction describes it: for compensation, “identify the ‘friendly’ number first and then add the difference” — the round number is the friendly one, and the adjustment is the difference you borrowed from it.
When to use it: Any subtraction where the number you’re taking away is within 1–3 of a round number.
Practice the Number Sense Behind These Tricks
Count up and bridge through 10 both depend on the same underlying skill: recognizing instantly which pairs of numbers add up to 10. When 7 and 3, 6 and 4, 8 and 2 are automatic — not recalled, just seen — the bridge move is effortless and counting up becomes faster.
That “complements to 10” instinct is exactly what Make 10 is built around. You’re scanning tiles to find pairs or groups that sum to ten. It’s a calm, no-score-pressure way to practice the same reflex the bridge trick uses. No account, no download.
Try Make 10 ↓ — No sign-up, play in your browser
For the multiplication version of this kind of shortcut thinking, mental multiplication tricks covers six methods that use the same break-apart and round-and-adjust logic.
Are These Tricks Worth Learning? (Honest Take)
Subtraction comes up constantly — splitting a check, estimating change, checking a sale price, counting days. A reliable method that doesn’t stall on borrowing makes those moments faster and less frustrating.
What it isn’t: a guaranteed path to sharper memory or any specific brain outcome. Arithmetic practice improves your arithmetic, which is genuinely useful. The broader claims about brain training are more complicated than popular coverage suggests. For an honest look at what the research says, brain games for seniors covers it directly.
Pick one trick this week — round and adjust is usually the fastest win — and use it when you’d normally reach for a calculator.
Just for fun — not medical advice.
Frequently Asked Questions
What’s the easiest way to subtract large numbers in your head?
Round and adjust (compensation) works well for most large numbers. Round the number you’re subtracting to the nearest 10 or 100, subtract that, then add back what you overshot. For 152 − 99, subtract 100 to get 52, then add 1 back: 53. One clean round number plus a small correction beats trying to borrow across multiple columns mentally.
How do I subtract when I have to borrow?
The bridge through 10 trick sidesteps borrowing entirely. Instead of working across digit columns, you use the nearest 10 as a stepping stone. Break the number you’re subtracting into two parts — one to reach 10, one to go further — and work in two small steps. 16 − 9 becomes 16 − 6 = 10, then 10 − 3 = 7. No borrowing, no column tracking.
Why is counting up easier than subtracting directly?
Subtraction asks you to remove and track what’s left. Counting up asks you to add toward a target — which is often a more natural mental motion, especially when the two numbers are close together. The difference between 58 and 64 is easier to find by adding up from 58 (you need just 6) than by borrowing down from 64.
Do these tricks work for 3-digit numbers?
Yes, especially round and adjust and left to right. For 324 − 198, round 198 to 200, subtract to get 124, then add 2 back: 126. For left to right on problems without borrowing: 476 − 231 → subtract 200 to get 276, subtract 30 to get 246, subtract 1 to get 245. The same structure scales.
How can I get faster at mental subtraction?
Use the tricks on real numbers, not practice sheets. Every time you estimate change, check a price difference, or calculate how many days until a date, pick one method deliberately. Short, frequent real-world use builds speed faster than sessions of worksheets. The bridge and count-up methods get faster as your “complements to 10” recognition sharpens — which a few rounds of Make 10 can help with in a low-stakes way.
Want a no-signup number puzzle to try right now? Make 10 is open in your browser.
More from the Make10s blog: how to improve your mental math · mental multiplication tricks · brain games for seniors · all posts
Just for fun — not medical advice.