Time Duration Calculator
Find the duration between two times.
24-hour format, HH:MM
24-hour format, HH:MM
Results update as you type.
How it works
A time duration calculator finds the elapsed time between a start clock time and an end clock time, returning the result as hours and minutes and also as decimal hours. It converts each time to minutes past midnight, subtracts, and when the end reads earlier than the start it adds a full day so an overnight span is measured correctly rather than showing a negative gap. This is the arithmetic behind every timesheet, and getting it right protects both pay and planning. Working out that a shift from the evening into the small hours lasted eight and a quarter hours is easy to fumble by hand, particularly across midnight, and errors there feed straight into wages, billable hours and rota coverage. A dependable time duration calculator removes that risk. The method uses minutes-past-midnight because clock time is not plain decimal — sixty minutes make an hour, not a hundred — so subtracting raw HH:MM values gives wrong answers. Converting to a single unit first sidesteps that. Shift workers, freelancers logging billable hours, payroll clerks and managers building rotas all reach for a time duration calculator, and the decimal-hours output drops directly into pay systems that multiply hours by a rate.
duration = end − start; if negative, add 24 hours (crosses midnight)
Each time is converted to total minutes since midnight, then the start is subtracted from the end. A negative result means the clock passed midnight, so 1,440 minutes — one full day — is added to make it positive. The minutes total is then split back into hours and minutes, and dividing by sixty gives decimal hours. Working in a single minute unit avoids mixing base-60 clock fields.
Source:Standard timekeeping arithmetic
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter start time and end time.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Duration updates instantly as you type — no button to press.
Frequently asked questions
How do I enter times?
Use 24-hour format as HH:MM, so nine in the morning is 09:00 and half past five in the afternoon is 17:30. To convert an afternoon or evening PM time, add twelve to the hour: 1:15 PM becomes 13:15, and 11:45 PM becomes 23:45. Midnight is 00:00. Entering times this way removes any AM/PM ambiguity from the calculation.
Does it handle overnight shifts?
Yes. When the end time is earlier than the start time, the calculator assumes the period ran past midnight and adds a full 24 hours, so a shift from 22:00 to 06:00 correctly reads as eight hours rather than a negative figure. This makes it reliable for night shifts, on-call windows and any span that crosses into the next day.
What are decimal hours and why use them?
Decimal hours express minutes as a fraction of an hour, so eight hours thirty minutes becomes 8.5 and fifteen minutes becomes 0.25. Payroll and invoicing systems use this form because you can multiply it straight by an hourly rate. The conversion is minutes divided by sixty, which is why 30 minutes reads as 0.5 rather than 0.30.
Does it account for unpaid breaks?
No. The result is the raw elapsed time between the two clock times. If a shift includes an unpaid lunch, subtract that break from the decimal-hours figure before applying a pay rate. For a 09:00 to 17:30 shift with a 30-minute break, the paid time would be 8.0 hours rather than the 8.5 shown.
Can I use this as a time card calculator?
Yes. Enter your clock-in as the start and clock-out as the end for each shift, and read the decimal hours for payroll. It handles single shifts including overnight ones. For a weekly total, run each day and add the decimal-hour figures, remembering to deduct any unpaid breaks before summing.