How to use the time calculator
- Choose Add / subtract time, Time duration or Work hours.
- Enter the time values. For shifts that cross midnight, select the overnight checkbox.
- Click the relevant Calculate button to display the result.
Time calculation formulas
Convert a duration to seconds with this formula:
For time addition, add the two durations in seconds. For subtraction, subtract the second duration from the first. A clock-time result wraps around the 24-hour day; a duration result keeps the full number of days.
Time conversion table
| Unit | Equivalent |
|---|---|
| 1 minute | 60 seconds |
| 1 hour | 60 minutes = 3,600 seconds |
| 1 day | 24 hours = 1,440 minutes |
| 1 week | 7 days = 168 hours |
Frequently asked questions
Can I add more than 24 hours?
Yes. Enter the amount in the days and hours fields. If a starting clock time is provided, the result also indicates how many days the clock time has moved forward or backward.
How do I calculate time across midnight?
In Time Duration or Work Hours mode, select the option that says the end time is on the next day. For example, 10:00 PM to 6:00 AM is 8 hours.
How are decimal hours calculated?
Divide the total number of seconds by 3,600. For example, 1 hour 30 minutes equals 1.5 decimal hours.
Can I subtract an unpaid break from work hours?
Yes. In Work Hours mode, enter the break in minutes. The calculator subtracts it from the gross shift duration and warns you if the break exceeds the shift length.
Are my time entries sent to the server?
The calculator calculations run in your browser. This tool's calculation code does not submit your entered times to the server.
This calculator is intended for general time arithmetic and planning. Payroll rules, rounding policies and paid-break regulations can vary by employer and jurisdiction.