Time Calculator
Add or subtract two time durations in hours, minutes and seconds. See the result in h:m:s and as total hours, minutes and seconds — handy for timesheets and scheduling.
Time Calculator
Duration 1
Hours
Minutes
Seconds
Duration 2
Hours
Minutes
Seconds
Result
4h 15m 0s
4.25 hours · 255 minutes
How It Works
Time arithmetic is easy to get wrong by hand because minutes and seconds roll over at 60, not 100 — 1 hour 45 minutes plus 1 hour 30 minutes is 3 hours 15 minutes, not 3 hours 75 minutes. This calculator avoids that by converting each duration entirely into seconds (hours × 3600 + minutes × 60 + seconds), performing the addition or subtraction on those totals, and then converting the result back into clean hours, minutes and seconds with proper carrying and borrowing. It also gives you the answer in several equivalent forms — the h:m:s breakdown, plus the total in hours (as a decimal), minutes, and seconds — because different tasks need different formats. It is useful for adding up timesheets and billable hours, working out total run or workout times, combining video/audio clip lengths, or finding the gap between two durations. Subtraction can produce a negative result, which the calculator shows with a minus sign.
Formula
Convert each duration to seconds (h×3600 + m×60 + s), add or subtract, then convert back to hours:minutes:seconds.
Frequently Asked Questions
How do I add hours and minutes correctly?
Remember minutes and seconds carry at 60, not 100. The calculator converts everything to seconds, adds, then converts back — so 1h 45m + 1h 30m correctly gives 3h 15m, not 3h 75m.
Can I subtract times to get a duration?
Yes — choose Subtract to find the difference between two durations. If the second is larger, the result is shown as a negative duration.
What is a decimal hour?
A duration expressed as a fraction of an hour — e.g., 90 minutes = 1.5 decimal hours. This format is common for timesheets and billing, and the calculator shows it alongside h:m:s.
What can I use this for?
Adding up timesheet or billable hours, totalling workout or run times, combining media clip lengths, computing elapsed time, or converting a duration between h:m:s and decimal hours.
Is this the same as a date difference calculator?
No — this adds and subtracts durations (spans of time). To find the exact gap between two calendar dates, use the Date Difference calculator; to shift a date by days/months, use the Add/Subtract Date calculator.