Use this free online time calculator to add or subtract two time durations given in hours, minutes, and seconds. It's perfect for combining work periods, cooking times, or workout intervals into one accurate total.
How to Use the Time Calculator
- Enter the First Duration in hours, minutes, and seconds.
- Choose Add or Subtract from the Operation dropdown.
- Enter the Second Duration in hours, minutes, and seconds.
- Click "Calculate" to see the combined result in hours, minutes, and seconds.
- Use "Clear" to reset both durations and start over.
How the Calculation Works
Adding times by hand is error-prone because minutes and seconds roll over at 60, not 100. The calculator avoids that by converting each duration into plain seconds first:
- Total seconds = hours × 3,600 + minutes × 60 + seconds.
- The two totals are added or subtracted.
- The answer is turned back into hours (seconds ÷ 3,600), the leftover into minutes (÷ 60), and what remains is seconds.
Hours are not converted into days, so a total of 30 hours is shown as 30h 0m 0s. That is usually what you want for timesheets and project logs.
Worked Examples
Adding two work shifts of 7h 45m 30s and 8h 20m 50s: the first is 27,930 seconds and the second 30,050 seconds. Together that is 57,980 seconds, which is 16 hours (57,600 s), 6 minutes (360 s) and 20 seconds. Result: 16h 6m 20s.
Subtracting 3h 40m 20s from 2h 15m 0s: 8,100 − 13,220 = −5,120 seconds. The calculator shows 1h 25m 20s with the note that the second time is longer, meaning you are 1 hour 25 minutes 20 seconds short.
Minutes to Decimal Hours
Payroll and billing systems often want hours as a decimal. Divide the minutes by 60 to convert. Common values:
| Minutes | Decimal hours |
|---|
| 6 | 0.1 |
| 15 | 0.25 |
| 20 | 0.333 |
| 30 | 0.5 |
| 45 | 0.75 |
| 50 | 0.833 |
A common mistake is reading 7h 30m as 7.30 hours. It is 7.5 hours. Writing 7.30 under-reports the time by 12 minutes.
Practical Tips
- To total more than two durations, add the first two, then enter the result as the first duration and add the next one.
- This tool works with lengths of time, not clock times. To find the time between 9:30 AM and 6:15 PM, use the Time Duration or Hours Calculator instead.
- You can type a decimal in any field. For example, 1.5 hours is treated as 1h 30m.
Frequently Asked Questions
The calculator shows the absolute value of the difference along with a note, "(negative duration: second time is longer)", so you know the second duration was actually longer than the first.
Yes. Any field left blank is treated as zero, so you can calculate with just hours, just minutes, or any combination you need.
The minute and second boxes step between 0 and 59, but you can type a larger value such as 90 minutes. Everything is converted to seconds before calculating, so 90 minutes is correctly treated as 1 hour 30 minutes. The hours field has no upper limit.
Add them two at a time. Calculate the first pair, type the result into the First Duration fields, enter the next duration as the second, and repeat until all are included.
The result is always given in hours, minutes and seconds, which suits timesheets and work logs. To express it in days, divide the hours by 24. For example, 50h is 2 days and 2 hours.