Time & Date
Add or subtract two time durations with precision down to the second.
Duration 1
Operation
Duration 2
Total Duration
4h 15m 0s
2h 30m 0s + 1h 45m 0s
Enter hours, minutes, and seconds for each duration. The result shows the combined time for addition, or the difference for subtraction. If the second duration is larger than the first in subtract mode, the result is zero.
A time calculator is a duration arithmetic tool that combines or compares two time periods (hours, minutes, seconds). Unlike a simple clock subtraction, it handles carry-over between units (e.g., 45 minutes + 30 minutes = 1 hour 15 minutes) automatically and displays results in both time format (HH:MM:SS) and decimal hours for flexibility.
The calculator converts each duration into total seconds, performs the arithmetic operation (addition or subtraction), then converts the result back into hours, minutes, and seconds. For addition, it sums the two totals; for subtraction, it finds the difference (clamped to zero if the second duration is larger). All unit carryover is handled automatically.
For addition: Total Seconds = (H₁ × 3600 + M₁ × 60 + S₁) + (H₂ × 3600 + M₂ × 60 + S₂)
For subtraction: Total Seconds = max(0, (H₁ × 3600 + M₁ × 60 + S₁) − (H₂ × 3600 + M₂ × 60 + S₂))Each duration is converted to seconds (hours × 3600, minutes × 60, plus seconds). Addition sums both totals; subtraction finds the positive difference. The result is then split back into hours (÷ 3600), remaining minutes (÷ 60), and remaining seconds.
| Input | Result | Notes |
|---|---|---|
| Duration 1: 2h 30m 0s, Duration 2: 1h 45m 0s, Operation: Add | 4h 15m 0s (4.25 hours, 255 minutes, 15300 seconds) | The durations add cleanly: 2 hours 30 minutes plus 1 hour 45 minutes equals 4 hours 15 minutes with no seconds remainder. |
| Duration 1: 3h 20m 30s, Duration 2: 1h 15m 45s, Operation: Subtract | 2h 4m 45s (2.08 hours, 124 minutes, 7485 seconds) | Subtraction handles unit borrowing: 30 seconds minus 45 seconds borrows 1 minute, making the calculation seamless. |
| Duration 1: 0h 45m 30s, Duration 2: 0h 30m 20s, Operation: Add | 1h 15m 50s (1.26 hours, 75 minutes, 4550 seconds) | Even sub-hour durations combine correctly; 45 minutes 30 seconds plus 30 minutes 20 seconds rolls over to 1 hour 15 minutes 50 seconds. |
Not in one step. To combine three durations, add the first two, then add the result to the third. Or convert all to minutes, sum them, and paste the total as minutes into the calculator.
The result is clamped to zero. Time cannot be negative in this context, so 1 hour minus 2 hours returns 0h 0m 0s.
No—enter decimal values in the hours field. The calculator treats any decimal as hours, so 1.5 in the hours field becomes 1 hour 30 minutes automatically (though it displays as 1h 0m).
Decimal hours are standard in time-tracking and payroll systems. 1 hour 15 minutes = 1.25 hours, which is easier to multiply for hourly rates or billing.
No. This calculator runs 100% in your browser. Your durations are never sent to a server or stored. Refresh the page and the inputs reset.
Yes. Convert the span to hours first (e.g., 1 full day = 24 hours) or use the total-hours output to track billable time. For complex schedules, spreadsheets may be clearer.