Time duration calculator for timesheets
Three jobs in one tool: total a list of durations, add or subtract two durations, or work out the time between two clock times. Everything is reported in hours and minutes and in decimal hours, which is the format most payroll and invoicing systems want. Overnight shifts are handled, and input can be written as 1:30, 90m or 1h 30m.
How to use the Time Duration Calculator
- Choose the mode: total a list, add or subtract two values, or measure between two clock times.
- Fill in the field that mode uses — the list, or the first and second values.
- Add an hourly rate if you want the time costed.
- Press Calculate duration.
Accepted formats
Durations can be written in whichever way you already write them, and they can be mixed in the same list:
| You type | It reads |
|---|---|
| 1:30 | 1 hour 30 minutes |
| 1:30:20 | 1 hour 30 minutes 20 seconds |
| 2h 15m | 2 hours 15 minutes |
| 1.5h | 1 hour 30 minutes |
| 45m | 45 minutes |
| 90 | 90 minutes — a plain number is read as minutes |
Clock times accept 24-hour form (17:45) or 12-hour with am/pm (5:45pm). For the time between two clock times, an end earlier than the start is assumed to cross midnight: 22:30 to 06:15 is 7 hours 45 minutes.
Worked example
A timesheet reading "1:30, 45m, 2h 15m" totals 90 + 45 + 135 = 270 minutes, which is 4 hours 30 minutes, or 4.50 decimal hours. At £22 an hour that is £99.00.
Decimal hours, and the mistake everyone makes
Payroll and invoicing systems almost always want decimal hours, and 4 hours 30 minutes is 4.5 — not 4.30. The conversion is minutes ÷ 60, so 15 minutes is 0.25, 20 minutes is 0.333, and 50 minutes is 0.833. Typing 4.30 into a timesheet when you worked 4 hours 30 minutes under-reports you by 12 minutes. The table below covers the common ones.
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.083 | 35 | 0.583 |
| 10 | 0.167 | 40 | 0.667 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.333 | 50 | 0.833 |
| 25 | 0.417 | 55 | 0.917 |
| 30 | 0.5 | 60 | 1.0 |
Practical notes
Subtracting a longer duration from a shorter one gives a negative result, shown with a minus sign rather than being clamped to zero — useful for checking a shortfall against contracted hours. Break deductions are not automatic: list them as negative values in the list, or subtract them in the two-value mode. The clock mode works on times of day only and ignores dates, so a shift that spans more than 24 hours should be entered as a duration rather than as two clock times.
Frequently asked questions
How do I convert minutes to decimal hours?
Divide by 60. Fifteen minutes is 0.25 hours, 30 minutes is 0.5 and 45 minutes is 0.75. Writing 4.30 for four and a half hours is a common and costly error.
Does it handle an overnight shift?
Yes. In clock mode, an end time earlier than the start is treated as crossing midnight, so 22:30 to 06:15 gives 7 hours 45 minutes.
Can I subtract breaks?
Yes. Enter the break as a negative value in the list, for example “8:00, -0:30”, or use the two-value mode and subtract.
What does a plain number mean?
Minutes. Type “90” for an hour and a half. Use 1:30 or 1.5h if you want to be explicit.
Privacy
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Last updated 2026-09-23.