How to Subtract Time in Hours and Minutes
Subtract the minutes first, then the hours — and when the minutes you're taking away are larger, borrow one hour as 60 minutes. So 8:00 − 1:45 becomes 7 hours 60 minutes − 1:45 = 6:15. If the result would go below zero, subtract the smaller from the larger and keep a minus sign.
The method, step by step
Subtracting time trips people up for one reason: minutes roll over at 60, not at 100. Once you borrow in sixties instead of tens, the arithmetic is ordinary. Work through these six steps in order.
- Write both values as
H:MM. Put the value you're subtracting from on top and the amount you're taking away underneath, hours over hours and minutes over minutes. A bare "45 minutes" becomes0:45. - Subtract the minutes. If the top minutes are the larger number, you're done in one move.
- Borrow if the minutes are short. Drop the top hours by 1 and add 60 — not 100 — to the top minutes.
- Subtract the hours. Pair the result with the minutes for the answer in
H:MM. - Handle a result below zero. Flip the subtraction, then write a minus in front.
- Convert to decimal if you need to check it or apply a pay rate. Divide the minutes by 60.
What does subtracting without borrowing look like?
Start with the easy shape: 7:45 − 2:15.
Minutes first: 45 − 15 = 30. Then hours: 7 − 2 = 5. The answer is 5:30 — 5 hours and 30 minutes, or 5.5 hours in decimal. No borrowing needed, because 45 is comfortably larger than 15.
This is the case where a phone calculator accidentally agrees with you: 7.45 − 2.15 = 5.30. That agreement is luck, not correctness, and it disappears the moment you need to borrow.
How do I borrow across the hour?
Take 8:00 − 1:45. You have zero minutes on top and need to take 45 away, so borrow one hour from the 8.
Rewrite 8:00 as 7 hours and 60 minutes. Now subtract normally: 60 − 45 = 15 minutes, and 7 − 1 = 6 hours. The answer is 6:15.
Sanity-check it in a different direction: from 1:45, adding 6 hours gets you to 7:45, and another 15 minutes reaches 8:00. Both routes land on 6:15.
One more: 9:20 − 5:35. The top minutes (20) are smaller than 35, so borrow — 9:20 becomes 8 hours and 80 minutes. Then 80 − 35 = 45 minutes and 8 − 5 = 3 hours, giving 3:45. In decimal that's 3.75 hours, not 3.45.
Worked examples you can check against
Every row below is a real subtraction, with the answer in H:MM, the same value in decimal hours, and what a plain base-10 calculator would have told you.
| Subtraction | Borrow? | Answer (H:MM) | Decimal | Plain calculator |
|---|---|---|---|---|
| 7:45 − 2:15 | No | 5:30 | 5.50 | 5.30 |
| 8:00 − 1:45 | Yes | 6:15 | 6.25 | 6.55 |
| 9:20 − 5:35 | Yes | 3:45 | 3.75 | 3.85 |
| 12:00 − 3:20 | Yes | 8:40 | 8.67 | 8.80 |
| 8:30 − 0:45 | Yes | 7:45 | 7.75 | 7.85 |
| 40:00 − 37:20 | Yes | 2:40 | 2.67 | 2.80 |
| 7:30 − 8:00 | n/a | −0:30 | −0.50 | −0.70 |
Look at the last column. Only the first row is even close, and the 8:00 − 1:45 row is off by 40 minutes — a plain calculator says 6.55, which reads as almost 6 hours 55 minutes when the truth is 6 hours 15 minutes. Repeat that mistake across a week of shifts and the timesheet is badly wrong.
Can a time subtraction be negative?
Yes, and negative totals are genuinely useful — they represent a shortfall rather than an error.
Say your week is supposed to total 40:00 and your timesheet adds up to 36:45. Because the amount you're taking away is larger, flip the subtraction: 40:00 − 36:45. Borrow to get 39 hours 60 minutes, then 60 − 45 = 15 and 39 − 36 = 3, so the gap is 3:15. Write it back as −3:15: you're 3 hours 15 minutes short.
Smaller version: 7:30 − 8:00 = −0:30. You worked half an hour less than a standard day. In decimal that's −0.50 hours, and at $22 an hour it's $11.00 less in that day's gross pay.
Plenty of tools refuse to show a negative time at all, which forces you to remember which way round the difference went. Hours keeps the sign, so a shortfall stays visible in your running total.
The all-minutes shortcut
If borrowing feels fiddly, convert both values to plain minutes, subtract, then convert back. Multiply the hours by 60 and add the minutes.
For 9:20 − 5:35: the top is 9 × 60 + 20 = 560 minutes and the bottom is 5 × 60 + 35 = 335 minutes. Subtract: 560 − 335 = 225 minutes. Convert back by dividing by 60: 225 ÷ 60 = 3 remainder 45, so 3:45 — the same answer borrowing gave.
This method also handles negatives without any special thought. 7:30 is 450 minutes and 8:00 is 480, so 450 − 480 = −30 minutes, which is −0:30. If you're comfortable with a running minute count, it's the fastest manual method there is.
Where you actually subtract time at work
Three situations account for nearly all real-world time subtraction.
Taking unpaid breaks off a shift
Elapsed time isn't paid time. An 8:30 shift with a 30-minute unpaid lunch is 8:30 − 0:30 = 8:00 paid. Add an unpaid 15-minute break and you're subtracting 0:45 in total: 8:30 − 0:45 = 7:45. Paid breaks stay in the total — don't subtract those.
Finding what's left in a budget
Suppose a client approved 20:00 for a project and you've logged 4:50, 6:35, and 3:40. Add them first: 4:50 + 6:35 = 11:25, and 11:25 + 3:40 = 15:05. Then subtract from the budget: 20:00 − 15:05, borrowing to 19 hours 60 minutes, gives 4:55 remaining. In decimal that's 4.92 hours — enough for one more half-day, not two.
Splitting regular hours from overtime
If a week totals 43:15 and the overtime threshold is 40 hours, subtract: 43:15 − 40:00 = 3:15 of overtime, with 40:00 at the regular rate. In decimal, 3:15 is 3.25 hours; at a $20 base rate, time-and-a-half is $30 an hour, so 3.25 × 30 = $97.50 in overtime pay. Our guide to calculating overtime works through a full week.
Overtime rules in the US generally require a premium for hours past 40 in a workweek for non-exempt employees, but the specifics depend on your state, your role, and how the workweek is defined. This is general US information, not legal or tax advice.
Why does a regular calculator get this wrong?
A phone calculator has no idea that 8:00 means eight hours. It reads 8.00 as a decimal number and borrows in hundredths, so 8.00 − 1.45 gives 6.55. Time borrows in sixtieths, which is why the real answer is 6:15.
You have two honest ways out. Convert every value to decimal hours before you calculate — 8:00 is 8.00 and 1:45 is 1.75, and 8.00 − 1.75 = 6.25, which is 6:15 — or use something that understands H:MM natively. Our explainer on what decimal hours are covers the conversion side, and calculating hours between two times handles the clock-in-to-clock-out case, including shifts that cross midnight.
Let the app do the borrowing
Hours subtracts times in H:MM without any borrowing on your part, shows negative totals instead of hiding them, flips to decimal in one tap, applies your hourly rate, and exports to CSV or PDF. Free, offline, no ads, no sign-in.
Frequently asked questions
How do you subtract hours and minutes?
Subtract the minutes first, then the hours. If the minutes you're taking away are larger, borrow one hour and add it to the top as 60 minutes. For 8:00 − 1:45, rewrite 8:00 as 7 hours 60 minutes: 60 − 45 = 15 and 7 − 1 = 6, so the answer is 6:15.
Why is 8:00 − 1:45 equal to 6:15 and not 6:55?
A plain calculator computes 8.00 − 1.45 = 6.55 because it works in tens. Minutes roll over at 60, so borrowing an hour gives you 60 extra minutes rather than 100. In decimal hours, 6:15 is 6.25 — not 6.15 and not 6.55.
Can a time subtraction be negative?
Yes — a negative result is a shortfall. If you owed 40:00 for the week and logged 36:45, the difference is −3:15. Work it out by subtracting the smaller value from the larger one, then add the minus sign.
How do I subtract a lunch break from a shift?
Convert the break to H:MM and subtract it from the elapsed shift time. An 8:30 shift with a 30-minute unpaid lunch is 8:00 of paid time; add an unpaid 15-minute break and you subtract 0:45 in total, leaving 7:45.