Time Duration Calculator
Add and subtract durations in hours, minutes and seconds, or measure the elapsed time between two clock times — including shifts that run past midnight, which is the case most calculators get wrong. Every answer also comes as a decimal in hours, minutes, seconds and days.
Calculate with time
The night shift problem
From 22:00 to 06:00 is eight hours. Subtract the numbers and you get minus sixteen. Every timesheet that has ever been wrong about a night shift got it wrong exactly here.
The fix is knowing whether the period crossed midnight, and no calculator can infer that from two clock times alone — 22:00 to 06:00 could be eight hours overnight or an impossible negative on the same day. So this one asks, with a checkbox, and adds the 24 hours when you say yes.
How to use this calculator
- Choose measuring between two clock times, or adding and subtracting durations.
- For clock times, enter them in 24-hour form and tick the box if the period runs overnight.
- For durations, fill in whichever of hours, minutes and seconds you need — empty boxes count as zero.
Decimal hours for timesheets
Payroll systems usually want decimal hours, not hours and minutes. Eight hours thirty is 8.5, but seven hours twenty is 7.333…, and rounding that by hand is where the money goes missing. Every result here includes the decimal figure alongside the clock form.
Frequently Asked Questions
How do I add and subtract time durations?
Switch to "add or subtract two durations", enter hours, minutes and seconds for each, and choose add or subtract. Empty boxes count as zero, and the result is given in clock form and as decimals.
How do I calculate hours worked across midnight?
Enter the start and end times and tick "this period crosses midnight". A shift from 22:00 to 06:00 is then correctly eight hours rather than a negative number.
How do I convert hours and minutes to decimal hours?
Divide the minutes by 60 and add them to the hours, so 7 hours 20 minutes is 7.33 hours. Every result here shows the decimal figure, which is what payroll systems normally want.
Can the result be negative?
When subtracting durations, yes, and it is shown with a minus sign. When measuring between two clock times a negative result usually means the period crossed midnight, so the calculator asks you to confirm rather than guessing.
What time format should I use?
24-hour, as HH:MM or HH:MM:SS. So 5:30pm is 17:30. This avoids the am/pm ambiguity around noon and midnight entirely.