Time Duration Calculator
Work out the time between two times, add or subtract durations, and total intervals in hours and minutes. Free, no sign-up, and it runs in your browser.
Dedicated page: /en/time-duration-calculator
Only used in the between-two-times mode.
Add up several intervals
Quick answer
A time duration calculator finds the elapsed time between a start time and an end time. From 9:00 AM to 5:30 PM is 8 hours 30 minutes, and minus a 30-minute unpaid break it is 8 hours, or 480 minutes, or 8.00 decimal hours.
About this Time Duration Calculator
Work out the time between two times, add or subtract durations, and total intervals in hours and minutes. It is one of the Work and School on ToolUstad, and like every tool here it runs entirely in your browser: nothing you type, paste or open is uploaded to a server, and there is no sign-up or usage limit.
What is a time duration calculator?
A time duration calculator finds the elapsed time between a start time and an end time, in hours, minutes and optionally seconds. It can also subtract an unpaid break and show the result as decimal hours, which is the format timesheets and payroll use. From 9:00 AM to 5:30 PM is 8 hours 30 minutes gross. Minus a 30-minute unpaid break, the net duration is 8 hours 0 minutes, which is 480 minutes, 28,800 seconds, and 8.00 decimal hours. The same page adds and subtracts durations, adds a duration to a clock time, and totals several intervals into one number.
The maths is one subtraction, but the units make it easy to get wrong by hand. Time is counted in groups of 60, and 24 hours make a day, so you regroup at 60, not at 10 or 100. That is why 8:30 plus 7:45 is 16:15, not 15:75, and why 7 hours 45 minutes is 7.75 hours, not 7.45. The calculator converts both clock times to minutes after midnight and subtracts, so the carrying is done for you, and every result is shown three ways at once: hours and minutes, total minutes, and decimal hours.
Add, subtract, and add to a clock
Adding and subtracting durations is the mode for totalling time: type two durations as hours and minutes, pick add or subtract, and get the exact result, plus the total in minutes and in decimal hours. Hours may exceed 24, so weekly totals work fine, and minutes must be 00 to 59. The add-to-clock mode answers the other common question: what time will it be after a duration? Enter a start time and a duration, and it gives the end time, wrapping past midnight. 11:00 PM plus 3 hours is 2:00 AM the next day.
Decimal hours and the 12-hour trap
Payroll, invoicing and spreadsheets need durations as decimal hours, because 7 hours 45 minutes cannot be multiplied by an hourly rate until it is written as 7.75. Divide the minutes by 60 to convert. The quarter hours are the ones worth memorising, since 15, 30 and 45 minutes give the exact figures 0.25, 0.50 and 0.75. The conversion table on the page lists the common values, and every result shows its own decimal figure to two places. The 12-hour clock has one trap worth knowing: 12:00 AM means midnight, and 12:00 PM means noon.
Best practices
- Use 24-hour times for night work: 22:00 to 06:00 is unambiguous, while 10:00 to 6:00 needs AM and PM to be right.
- Subtract only unpaid breaks: a paid break is still work time, and subtracting it understates the hours.
Common mistakes to avoid
- Writing 8.30 for 8 hours 30 minutes: 30 minutes is 0.50 hours, so 8 hours 30 minutes is 8.50, not 8.30.
- Forgetting the midnight wrap: a night shift that ends earlier on the clock than it starts is not a negative number.
Who is the time duration calculator for?
Hourly workers totalling a shift, managers adding up a week of intervals, freelancers billing by the hour, and anyone who needs to know how long something took, what time it will end, or how several spans add up.
Related terms: hours between two times, time difference calculator, add hours and minutes, subtract time, decimal hours converter, elapsed time calculator, overnight shift calculator, minutes to hours.
Clock times are compared as entered. The calculator does not adjust for time zones or daylight saving changes.
Learn: how to use the Time Duration Calculator
- Pick a mode: between two times, add or subtract durations, or add a duration to a clock time.
- Enter the times or durations, and an unpaid break if one applies.
- Read the duration in hours and minutes, total minutes, seconds and decimal hours.
Features
- Time between two times, with overnight spans handled
- Unpaid break deduction in the between-times mode
- Add or subtract two durations in H:MM
- Add a duration to a clock time, wrapping past midnight
- Add up to 8 intervals into one total
- 12-hour and 24-hour formats
- Minutes-to-decimal-hours conversion table
Worked example
From 9:00 AM to 5:30 PM is 8 hours 30 minutes gross. Minus a 30-minute unpaid break, the net duration is 8 hours 0 minutes, which is 480 minutes, 28,800 seconds, and 8.00 decimal hours. A night shift from 10:00 PM to 6:00 AM reads as 8 hours, not a negative number, because the end time is read as the next day.
Frequently asked questions
How do I calculate the time between two times?
Convert both to 24-hour format and subtract the start from the end. If the end is earlier than the start, the range crosses midnight: add 24 hours to the end time first.
What are decimal hours?
Hours written as a decimal fraction, which is what payroll and invoicing use. Divide the minutes by 60: 7 hours 45 minutes is 7.75 hours, not 7.45. The quarter hours are 15 minutes is 0.25, 30 is 0.50, and 45 is 0.75.
How do I add 8:30 and 7:45?
Add the minutes and the hours separately and carry every 60 minutes into one hour. 8:30 plus 7:45 is 16:15, not 15:75, because 75 minutes is 1 hour 15 minutes. In decimal hours that is 16.25. The calculator does the carrying for you.
What time is 2 hours 30 minutes after 9:00 AM?
11:30 AM. Add the duration to the start time and wrap past midnight if needed: 11:00 PM plus 3 hours is 2:00 AM the next day. The add-to-clock mode on this page does exactly that.
Does the calculator handle overnight shifts?
Yes. A span that ends earlier on the clock than it starts is treated as finishing the next day, so 10:00 PM to 6:00 AM reads as 8 hours rather than minus 16. The same rule applies to every interval in the multi-interval total.
What is the difference between elapsed time and paid hours?
Elapsed time is the full span between two times. Paid hours subtract unpaid breaks, and then apply your workplace rounding and overtime rules. This calculator gives you the elapsed time and the break-adjusted time; your contract decides what is paid.
Why does 12:00 AM mean midnight?
On a 12-hour clock, 12:00 AM is midnight at the start of a day and 12:00 PM is noon in the middle of it, which is the reverse of what the numbers suggest, since 12 AM comes before 1 AM and 12 PM comes before 1 PM.
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