Time Duration Calculator

Utility instrumentAnswer first. Adjust only what matters.

Input

Start Time

Accepts 12h or 24h format, e.g., 09:00 or 9:00 AM

End Time

Accepts 12h or 24h format, e.g., 17:30 or 5:30 PM

24-hour output

Controls output format only

Include seconds

Show seconds in results

Crosses midnight

End time is on the following day

Total Duration

8h 30m

Decimal Hours

8.50hrs

Total Minutes

510min

Day %

35.4%

8 hours 30 minutes. 8.50 decimal hours. 510 total minutes

Breakdown

Hours and minutes: 8h 30m
Decimal hours: 8.50
Total minutes: 510
Total seconds: 30,600
Day percentage: 35.4%
Start: 09:00
End: 17:30

Formula: Time format: 24-hour · Cross midnight: Enabled

Result story · Elapsed time

8h 30m

This is the exact elapsed span from 09:00 to 17:30 on the same day.

Start: 09:00
End: 17:30
Share of a day: 35.4%

What this tells you8.50 decimal hours is the useful form for time sheets and pay calculations; 510 minutes is the exact whole-minute equivalent.

Assumptions and limitsTime format: 24-hour · Cross midnight: Enabled

Turn the span into work hoursContinue with breaks, payable time, and a workday interpretation.

Timeline

Before: 9

Duration: 8.5

After: 6.5

Formula

End Time − Start Time = Duration

If end time is earlier than start time and 'Crosses midnight' is enabled, 24 hours are added to the end time. Equal start and end times produce zero duration.

Example: Standard Work Day

Start09:00

End17:30

Result8h 30m

Tips

The parser accepts both 12-hour and 24-hour formats regardless of the output setting.
Enable 'Crosses midnight' for overnight shifts or events.
Enable 'Include seconds' for precise timing.
Results update automatically as you type.

Frequently Asked Questions

How do I calculate overnight duration?

Enable the 'Crosses midnight' option. This tells the calculator that the end time is on the following day, so it adds 24 hours to the end time before calculating the difference.

What if the end time is earlier than the start time?

If 'Crosses midnight' is enabled, the calculator assumes the end time is the next day. If disabled, it will show an error asking you to enable 'Crosses midnight'.

Can I use AM/PM format?

Yes. The parser accepts both 12-hour (AM/PM) and 24-hour formats regardless of the output format setting. The format toggle only controls how results are displayed.

How accurate is the calculation?

The calculation is exact to the second. Enable 'Include seconds' to see seconds in the result. The internal calculation uses integer seconds to avoid floating-point errors.

Can I share my calculation?

Yes. Click 'Share Link' to copy a URL that includes your inputs. Anyone with the link will see the same calculation.

Related Tools

Hours Calculator

Calculate total hours from start and end times.

Add Time Calculator

Add hours and minutes to a time.

Subtract Time Calculator

Subtract hours and minutes from a time.

Work Hours Calculator

Track work hours with breaks and overtime.

Last reviewed: July 17, 2026