Date & Time · Guide
How to Calculate Hours Between Two Times
Start time, end time, minus the break. Here is the method that works every time — even past midnight.
Want the answer for your own numbers? Use the free Time Calculator — it does every step below for you.
The quick method
Working out the time between two times takes three steps. You can do it on paper in under a minute.
- Write both times in 24-hour form. 5:15 pm becomes 17:15.
- Subtract the start from the end. Do the hours and the minutes separately.
- Borrow if the minutes go negative. Take 1 hour away and add 60 minutes.
Example: 8:45 am to 5:15 pm
17:15 − 8:45. The minutes give 15 − 45, which is negative.
Borrow one hour: 16 hours 75 minutes − 8 hours 45 minutes.
8 hours 30 minutes
Taking off a lunch break
Most time clocks with lunch breaks record four punches: in, out for lunch, back from lunch, and out. You can either add up the two work blocks or subtract the break from the full span. Both give the same answer.
Example: one shift, two blocks
In 8:45, out to lunch 12:30, back 1:00, out 5:15.
Morning: 8:45 to 12:30 = 3 h 45 min. Afternoon: 1:00 to 5:15 = 4 h 15 min.
Total worked: 8 hours exactly
Check it the other way: the full span is 8 h 30 min, and the break was 30 minutes. Same answer.
Planning an 8-hour shift
Need to know when an 8-hour shift ends? Add 8 hours plus any unpaid break to the start time.
| Start | Unpaid break | Clock out at |
|---|---|---|
| 7:00 am | 30 min | 3:30 pm |
| 8:00 am | 30 min | 4:30 pm |
| 8:30 am | 1 hour | 5:30 pm |
| 9:00 am | 45 min | 5:45 pm |
| 10:00 pm | 30 min | 6:30 am (next day) |
Night shifts that cross midnight
When the end time is smaller than the start time, the shift ran past midnight. Add 24 hours to the end time, then subtract.
Example: 10:00 pm to 6:30 am
22:00 to 6:30. Add 24 to the end: 30:30 − 22:00.
8 hours 30 minutes
The time calculator does this automatically — pick "Time between two clock times" and it spots the midnight crossing for you.
Turning hours into decimal hours for payroll
Pay is worked out in decimal hours, not hours and minutes. Divide the minutes by 60:
- 8 h 30 min = 8 + 30/60 = 8.5 hours
- 7 h 45 min = 7.75 hours
- 6 h 20 min = 6.33 hours (not 6.20!)
That last one catches a lot of people. Writing 6.20 on a time card underpays you by 8 minutes.
Minutes to decimal hours: quick chart
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.08 | 35 | 0.58 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 25 | 0.42 | 55 | 0.92 |
| 30 | 0.50 | 60 | 1.00 |
Only 15, 30 and 45 minutes give tidy decimals. Everything else repeats, so keep two decimal places.
Adding up a weekly time card
| Day | In | Out | Break | Hours |
|---|---|---|---|---|
| Monday | 8:45 | 17:15 | 30 min | 8.00 |
| Tuesday | 9:00 | 17:30 | 30 min | 8.00 |
| Wednesday | 8:30 | 18:00 | 45 min | 8.75 |
| Thursday | 9:15 | 17:00 | 30 min | 7.25 |
| Friday | 8:00 | 16:20 | 30 min | 7.83 |
| Week total | 39.83 | |||
Convert each day to decimals first, then add. Adding hours and minutes directly works too, but it is easy to slip when the minutes pass 60.
Common mistakes
- Mixing am and pm. Use 24-hour time while you calculate.
- Forgetting the break. Paid breaks stay in; unpaid breaks come out.
- Treating minutes as decimals. 30 minutes is 0.5 hours, not 0.30.
- Rounding too early. Round only the weekly total, if at all.
Worked overtime? Our guide to time and a half shows how to price those hours.
In Excel or Google Sheets
Put the start time in A2 and the end time in B2, both as times.
- Hours as a decimal:
=(B2-A2)*24 - Shifts past midnight:
=MOD(B2-A2,1)*24— MOD wraps a negative result round to the next day. - Minus a 30-minute break:
=MOD(B2-A2,1)*24-0.5 - Weekly total as hours and minutes: add the times and format the cell as
[h]:mm. The square brackets stop the total resetting after 24 hours.
Can your employer round your time?
In the US, federal rules allow employers to round clock times to the nearest 5, 6 or 15 minutes — but only if the rounding is neutral, so that over time it does not always favour the employer. With 15-minute rounding, 8:07 rounds to 8:00 and 8:08 rounds to 8:15. If you think rounding always cuts your hours, keep your own record of real times.
Frequently asked questions
Convert both times to 24-hour form and subtract the start from the end. If the minutes go negative, borrow one hour as 60 minutes. 8:45 to 17:15 is 8 hours 30 minutes.
Find the time from clock-in to clock-out, then subtract the unpaid break. 8:45 am to 5:15 pm with a 30-minute lunch is 8 hours of work.
Add 8 hours plus any unpaid break to your start time. Starting at 7:00 am with a 30-minute unpaid lunch, the shift ends at 3:30 pm.
With the start time in A2 and end time in B2, use =(B2-A2)*24 for decimal hours. For shifts that cross midnight, use =MOD(B2-A2,1)*24.
In the US, yes, to the nearest 5, 6 or 15 minutes, as long as the rounding is neutral and does not consistently reduce the hours you are paid for. Rules outside the US vary.
Sources and further reading
- 29 CFR § 785.48 — Use of time clocks (Cornell LII) — the US rule allowing neutral rounding of clock times