Time Duration Calculator
Hours and minutes between two times, with totals and decimal hours for timesheets.
What it does
Clock subtraction borrows sixty, not a hundred, which is why plain mental math slips. The safe path converts both times to minutes after midnight, subtracts, and converts back to hours and minutes. Ends before starts roll into the next day for night shifts.
The tool above does exactly that. Enter start and end to get the span as hours and minutes, the total minutes, and decimal hours for timesheets and billing.
Breaks sit outside the span. Subtract lunch and pauses separately, since paid and worked time differ on most rosters.
How to use
- Enter the start time in 24 hour or AM/PM form, per your browser picker.
- Enter the end time. Earlier than start means overnight.
- Read hours and minutes for planning, decimal hours for pay math.
- Subtract breaks by hand or run the tool twice around the break.
Formula
- minutes after midnight
- Hours times 60 plus minutes for each clock time.
- 1440
- Minutes per day, added for overnight spans.
- / 60
- Minutes to decimal hours.
The 1440 is a full day in minutes and handles night shifts crossing midnight. Identical start and end read as zero; overnight shifts ending exactly at the start time need the day noted alongside.
Worked example
Example: 09:15 to 17:45
A workday from quarter past nine to quarter to six.
- Start in minutes: 9 x 60 + 15 = 555.
- End in minutes: 17 x 60 + 45 = 1065.
- Subtract: 1065 - 555 = 510 minutes.
- Back to hours: 510 / 60 = 8 h with 30 left, so 8 h 30 min.
- Decimal: 510 / 60 = 8.50 h. Minus a 30 min lunch, paid 8.00 h.
Reference table
| Span | Minutes | Decimal |
|---|---|---|
| 15 min | 15 | 0.25 h |
| 30 min | 30 | 0.50 h |
| 45 min | 45 | 0.75 h |
| 7 h 30 min | 450 | 7.50 h |
| 8 h 30 min | 510 | 8.50 h |
Limits
- Minute precision. Seconds round once at the end.
- Identical times read as zero, not 24 hours.
- Daylight saving jumps sit outside clock math.
- Breaks and unpaid time need separate subtraction.
Common mistakes
- Subtracting times like decimals. 17:45 minus 09:15 is not 8.30.
- Forgetting the overnight roll for shifts past midnight.
- Rounding each leg before adding instead of once at the end.
- Billing decimal hours from rounded clock times instead of exact ones.
- Leaving breaks inside paid time.
Try it yourself
Quick checks. Answers sit tucked under each question.
13:00 to 21:30?
510 minutes: 8 h 30 min, or 8.50 decimal hours.
22:00 to 06:00?
Overnight: 480 minutes, 8 h 00 min.
Questions
How do overnight shifts work here?
An end earlier than the start adds 24 hours. A 22:00 to 06:00 shift reads 8 hours.
What are decimal hours for?
Pay math. Multiply decimal hours by the hourly rate directly: 8.50 h at $20 is $170.
How do I subtract lunch?
Run start to lunch, then lunch end to finish, and add the two spans. Or subtract break minutes from the total.
Does it handle seconds?
No, minutes are the finest step. Round seconds once at the end for payroll.
Why 24 hour input?
It removes AM/PM mixups. Most browsers accept both forms in the time picker.