Time Calculator — Add, Subtract and Calculate Time Duration Free
Add or subtract hours, minutes and seconds from any time, or find the exact duration between two times. Handles overnight shifts and midnight crossing. Instant, free, no sign-up.
Last updated: June 2026
Result time
- 12-hour
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- 24-hour
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Result time
- 12-hour
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- 24-hour
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Duration
- Hours, minutes, seconds
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- Decimal hours
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- Total minutes
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Common uses
Shift duration: Start 9:00 AM, End 5:30 PM = 8 hours 30 minutes.
Travel time: Depart 11:45 PM, arrive 6:20 AM (next day) = 6h 35m.
Billable hours: 2h 15m + 3h 45m + 1h 30m = 7h 30m.
About this tool
Add, subtract and measure time the easy way
Working with clock time by hand is error-prone. Minutes roll over at 60, not 100, and adding a couple of hours can push you past midnight into the next day. This time calculator handles all of that for you. Pick a mode, enter your values, and the answer appears instantly in both 24-hour and 12-hour format, with a clear note when the result lands on a different day.
The Add Time and Subtract Time modes are perfect for questions like "what time will it be 3 hours 20 minutes from now?" or "if a meeting ends at 4:15 PM and ran 90 minutes, when did it start?". The Duration Between mode answers the opposite question: how long is the gap between two times? It gives you the hours and minutes, the decimal hours your timesheet wants, and the total minutes.
Overnight periods are handled cleanly. A shift that starts at 11:45 PM and ends at 6:20 AM is recognised as crossing midnight, and the explicit Next day toggle makes the intent unmistakable. Whether you are logging billable hours, planning travel, calculating a work shift or just settling a "how long until" question, the calculation is instant, free and completely private to your browser.
How it works
Three quick steps — no account, nothing uploaded to a server.
Choose a mode
Add time, subtract time, or measure the gap between two times.
Enter your values
Type a start time and the hours and minutes to add, or two times.
Read the result
See the answer in 12-hour and 24-hour format instantly.
FAQ
Frequently asked questions
How do I add hours and minutes to a time?
Pick the Add Time tab, set your starting time, then type how many hours, minutes and seconds you want to add. The result updates instantly in both 24-hour and 12-hour format. For example, 3:30 PM plus 2 hours 45 minutes gives 6:15 PM. If the total crosses midnight, the result shows a +1 day note so you know it lands on the next day.
How do I calculate the duration between two times?
Use the Duration tab, enter a start time and an end time, and the calculator shows the gap in hours, minutes and seconds, as decimal hours (handy for billing) and as total minutes. If your end time is earlier than your start time, the tool assumes the period crosses midnight, which is exactly what you want for an overnight shift.
Does it handle overnight shifts and midnight crossing?
Yes. In the Duration tab there is a Next day toggle for shifts that clearly run into the next calendar day. Even without it, if the end time is before the start time the calculator treats it as crossing midnight, so a shift from 11:45 PM to 6:20 AM correctly returns 6 hours 35 minutes.
What are decimal hours and why do they matter?
Decimal hours express a duration as a single number instead of hours and minutes. 8 hours 30 minutes becomes 8.5 hours. Most timesheets, payroll systems and freelance invoices want decimal hours, so the Duration tab shows them alongside the normal hours-and-minutes result.
Is the time calculator free and private?
Completely. There is no sign-up, no limit and no cost. Every calculation runs in your browser using plain JavaScript, so the times you enter are never uploaded or stored anywhere. You can close the tab knowing nothing was sent to a server.
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