Time Duration Calculator

Measuring elapsed time

Time arithmetic is base-60, which is why doing it in your head goes wrong. 9:45 to 17:20 isn't 7.75 hours or 8 hours 25 minutes — it's 7 hours 35 minutes.

The reliable method is to convert both times to minutes since midnight, subtract, then convert back. That's what happens here, and it's why the shift-crossing case works without any special handling.

Overnight shifts

When the end time is earlier than the start time, the span is treated as crossing midnight. A shift from 22:00 to 06:00 is eight hours, not a negative number.

The one case this can't distinguish is a span longer than 24 hours. If you need to measure across multiple days, use a date calculator instead — times alone carry no information about which day they belong to.

Decimal hours for timesheets

Payroll systems almost universally want decimal hours rather than hours and minutes. The conversion is minutes ÷ 60:

Rounding errors here compound. Twelve entries rounded to the nearest quarter hour can drift by a meaningful amount across a month, so check whether your employer rounds and in which direction.

Unpaid breaks

If your break is unpaid, subtract it — a 30-minute lunch turns an eight-hour day into 7.5 paid hours. Rules vary by jurisdiction: many require a break after a certain number of consecutive hours, and whether it's paid depends on local law and contract.