How to use Time Duration Calculator
Enter times on a 24-hour clock and specify whether the end occurs on the same day or the next day. The result gives both hours-and-minutes notation and decimal hours, which are useful for timesheets.
One hour and 30 minutes is 1.5 decimal hours, not 1.30 hours. This tool performs clock arithmetic without timezones, daylight-saving transitions or dates. Choose another method for travel across timezones.
The formula
Duration in minutes = end minutes − start minutes
Add 1440 minutes if the end is on the next day
A worked example
Start time: 09:00 · End time: 17:30 · End date: Same day
Time elapsed: 8h 30m
Clock-time arithmetic without timezone or daylight-saving adjustments.
Questions about this calculation
How do I calculate 10 pm to 6 am?
Enter 22:00 and 06:00, then select “Next day”.
What are decimal hours?
Minutes expressed as a fraction of 60; 30 minutes is 0.5 hours.
Formula checks: 2026-10-08. Assumptions & corrections.