How it works
Adding times by hand is error-prone because minutes and seconds roll over at 60, not 100. This calculator turns each duration into seconds, adds or subtracts them, and converts the result back, so carries are always right. Empty boxes count as zero, and hours can be larger than 24.
total seconds = hours × 3,600 + minutes × 60 + seconds result = A ± B, then hours = ⌊s ÷ 3,600⌋, minutes = ⌊(s mod 3,600) ÷ 60⌋, seconds = s mod 60Worked example. 2:45:50 + 1:20:30. Seconds: 50 + 30 = 80 → 1 minute 20 seconds. Minutes: 45 + 20 + 1 = 66 → 1 hour 6 minutes. Hours: 2 + 1 + 1 = 4. Result: 4:06:20, which is 4.1056 hours or 246.33 minutes. Subtracting instead, 2:45:50 − 1:20:30 = 1:25:20.
Decimal hours
Timesheets and payroll often need decimal hours: 4 h 6 min 20 s = 4 + 6/60 + 20/3,600 = 4.1056 h. Note that 1.5 hours is 1 h 30 min, not 1 h 50 min — a common payroll mistake.
| Minutes | Decimal hours |
|---|---|
| 15 min | 0.25 |
| 20 min | 0.333 |
| 30 min | 0.5 |
| 45 min | 0.75 |
| 50 min | 0.833 |
Typical uses
- Adding lap or split times in running and swimming.
- Totalling video or audio clip lengths for an edit.
- Summing flight segments or layovers.
- Subtracting a break from a shift — or use hours between two times with start and end clock times.
If the second duration is longer when subtracting, the result is shown as negative. For dates rather than durations, use the days from today calculator.