How to Calculate Hours for Overnight and Night Shifts

The work hours calculator handles shifts that cross midnight automatically. This guide shows the method behind it, plus the two nights a year when the clock gives the wrong answer.

Why subtraction breaks after midnight

A shift from 11:00 PM to 7:30 AM is 23:00 to 7:30 in 24-hour time. Subtract the usual way and you get a negative number, because the end time is on the next day.

The fix: add 24 hours to the end time

If the end time is earlier than the start, add 24 hours to it before subtracting. 7:30 becomes 31:30, and 31:30 − 23:00 is 8 hours 30 minutes. Then take off any unpaid break, exactly as for a day shift.

12-hour shifts

A 7:00 PM to 7:00 AM shift is 12 hours on the clock: 7:00 + 24 = 31:00, and 31:00 − 19:00 = 12:00. With a 30-minute unpaid meal break, that's 11 hours 30 minutes, or 11.5 hours. Three of those in a week is 34.5 hours; four is 46, which is 6 hours over the federal 40-hour overtime line.

Which week the hours count toward

Under the US federal rule, hours count toward the workweek in which they're worked. If a night shift starts on the last day of your workweek and ends on the first day of the next, the hours after midnight belong to the new week. That matters for overtime, which is worked out one week at a time — see how to calculate overtime.

The two daylight-saving nights

On the night the clocks go back, a shift that spans 2:00 AM is an hour longer than the clock says. In the US that's the first Sunday in November: a 10:00 PM to 6:00 AM shift on November 1, 2026 is 9 hours worked, not 8. On the night the clocks go forward — the second Sunday in March — the same shift is 7 hours, as on March 14, 2027.

You're owed pay for the hours you actually worked, so it's worth checking your timesheet on those nights. The work hours calculator measures clock time, so add or subtract that hour yourself. Places that don't change their clocks — most of Arizona, Hawaii, and since 2026 British Columbia — have no adjustment to make.

Rotating schedules

On rotating shifts, work out each shift on its own and total the week in hours and minutes before converting to decimal. How to total a weekly timesheet covers the weekly total, and the work hours calculator takes a mix of day and night shifts in one sheet.