Time Calculator
Calculate the duration between two clock times, or add and subtract hours, minutes and seconds. Results include practical time units and decimal hours.
Calculate time between two clock times
Add or subtract time
What the results mean
The duration result shows the answer as days, hours, minutes and seconds, plus total minutes, total seconds and decimal hours. Decimal hours are useful for timesheets and billing: 1 hour 30 minutes is 1.5 hours.
How time calculations work
Clock time is based on 60 seconds per minute and 60 minutes per hour. The duration calculator subtracts the start timestamp from the end timestamp. When an interval crosses midnight, the next-day option adds 24 hours before calculating.
For add/subtract calculations, the entered hours, minutes and seconds are converted to one total number of seconds, the operation is applied, and the result is converted back into clock time and day offset. This avoids treating minutes as decimal hours.
Common uses
- Find elapsed time for work shifts, study sessions, travel, workouts or appointments.
- Convert a duration to decimal hours for timesheets or invoices.
- Add a planned duration to a start time to estimate an end time.
- Subtract a duration from a deadline or scheduled time.
Frequently asked questions
How do I calculate the time between two times?
Enter the start and end clock times and calculate. When the interval crosses midnight, use the next-day option if the end clock time is earlier than the start time.
What is the duration from 9:30 AM to 5:15 PM?
It is 7 hours 45 minutes, which is 7.75 decimal hours.
Why do minutes not work like decimal numbers?
An hour contains 60 minutes, not 100. Therefore 2 hours 30 minutes equals 2.5 hours, while 2 hours 45 minutes equals 2.75 hours.
Can the calculator handle times across midnight?
Yes. Enable the next-day option in the duration calculator when the end time belongs to the following day.
Does this calculate dates and time zones?
No. This tool focuses on clock-time arithmetic and elapsed time within a 24-hour cycle. Use a dedicated date or time-zone calculator when calendar dates or time-zone changes are part of the problem.
Related tools
Need calendar-aware working time rather than simple clock arithmetic? Use the Business Hours Calculator to count business hours across dates, holidays and custom work schedules.
Method & reference notes
The calculator uses straightforward elapsed-time arithmetic rather than assumptions about time zones, daylight-saving changes, leap seconds or calendar dates. For calendar-aware calculations, business days, holidays, or custom work schedules, use the Business Hours Calculator.
Related reference material: Timeanddate time-duration calculator and Calculator.net time calculator.