Time CalculatorAdd or subtract hours, minutes and seconds
Add and subtract durations in hours, minutes and seconds, or find the clock time before or after any duration, with the total in h:mm:ss, decimal hours, minutes and seconds.
- Carries & borrows automatically
- Seconds precision
- Clock-time mode
- Results over 24 h
Time calculator
Total duration
0:00:00
How the durations stack up
Added durations are solid and subtracted ones are hatched. The marker shows the total.
How do you add or subtract time?
Add hours to hours, minutes to minutes and seconds to seconds. Every 60 seconds carry into a minute and every 60 minutes into an hour. When subtracting, borrow 60 from the next column. For example, 2:45:00 + 1:30:30 − 0:20:00 = 3:55:30, or 3.93 hours. To add a duration to a clock time, 9:45 AM + 3 h 50 min = 1:35 PM.
Worked example: adding times by hand
2 h 45 min 00 s+ 1 h 30 min 30 s= 3 h 75 min 30 s → 75 min = 1 h 15 min → 4:15:30− 0 h 20 min 00 s → 3:55:30 (= 3.925 hours)Time unit conversions
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 minute | 60 | 1 | 0.0167 |
| 1 hour | 3,600 | 60 | 1 |
| 1 day | 86,400 | 1,440 | 24 |
| 1 week | 604,800 | 10,080 | 168 |
| 1 year (365 days) | 31,536,000 | 525,600 | 8,760 |
Everyday uses
Workout and race splits
Add lap or interval times to get a total, or subtract to compare personal bests.
Video, audio and podcast lengths
Total several clips, or work out how much time is left after trimming.
Billable sessions
Add up sessions across a project, then convert to decimal hours for the invoice.
Cooking and baking
Start at 4:40 PM with 2 h 15 min of prep and baking? Clock mode says 6:55 PM.
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Manzoor Ahmad
Calculator Developer · Founder of DexoCalc
I’m a pharmacist turned web developer with 13+ years of experience building web tools. This calculator works in whole seconds internally, so carrying and borrowing never builds up rounding errors. I tested it against negative totals, 24-hour-plus durations and day-crossing clock times.
Published · Last reviewed · Author profile · Report an issue
Time calculator: frequently asked questions
Add the minutes, carry every 60 minutes into an hour, then add the hours. Enter each duration as a row above and the calculator totals them, including seconds.
Tap the + button on a row to switch it to −. The calculator borrows across units automatically and shows a negative result if the subtractions exceed the additions.
Use ‘Clock time ± duration’. Enter the current time and the duration. 9:45 AM + 3 h 50 min = 1:35 PM. It also tells you if the result falls on another day.
Divide the minutes by 60 and the seconds by 3,600, then add them to the hours. 3:55:30 = 3 + 55/60 + 30/3600 = 3.925 hours. It’s shown automatically.
Yes. Durations aren’t clock times, so 30:15:00 is valid. The ‘days + time’ tile also shows it as 1 day 6:15:00.
The hours calculator finds the time between two clock times. This calculator adds and subtracts durations you already have.
Sources & references
- Time and Frequency Division, National Institute of Standards and Technology
- The International System of Units (SI): the second, BIPM
Durations are exact. Clock-time results ignore daylight-saving changes.