How this instrument works
This calculator adds a shift's length and any unpaid break time onto a start time, using 24-hour clock arithmetic, and returns the exact end time. It also flags whether the shift rolls past midnight into the next calendar day, which matters for anyone scheduling or clocking overnight shifts.
The default numbers model the most common shift shape: an 8-hour shift with a 30-minute unpaid break, which totals 8.5 hours from clock-in to clock-out even though only 8 hours are actually worked. Both numbers are editable — a 6.5-hour shift with no break, or a 12-hour shift with two breaks combined into one number, work exactly the same way.
Because the arithmetic wraps at 24 hours, a shift that starts late in the evening and runs past midnight is handled correctly: the end time shown is the clock time on the following calendar day, and the calculator tells you explicitly how many days later that is.
- Enter the shift's start time as an hour (0–23) and minute.
- Enter the shift length in hours — decimals like 6.5 are fine.
- Enter any unpaid break time in minutes; leave it at 0 if there's no break.
- Read the end time (hour and minute) and whether it falls on a later calendar day.
Worked example — an 8-hour retail shift with a lunch break
A retail worker clocks in at 7:00 AM for an 8-hour shift with a 30-minute unpaid lunch break. Enter start hour 7, start minute 0, shift length 8, and break 30. Total time from clock-in to clock-out is 8.5 hours, and the calculator returns an end time of 15:30 — 3:30 PM — the same day.
Change the start time to 22:30 (10:30 PM) with the same 8-hour shift but a 45-minute break, and the total 8.75 hours pushes the end time past midnight: the calculator returns 7:15 the next calendar day, flagging it as one day later than the start.
Questions
Does the break time get added to the shift length or subtracted from it?
Added. This calculator treats the break as unpaid time on the clock — time you're present but not working — so it lengthens how long you're actually at the workplace, from clock-in to clock-out, beyond just the working hours themselves.
How does it handle a shift that runs past midnight?
The internal math works in total minutes and wraps every 24 hours, so an overnight shift's end time is still shown correctly as a 0–23 hour. A separate 'days later' figure tells you it's the next calendar day (or later) rather than leaving you to guess from the clock time alone.
Can I use decimal hours for the shift length?
Yes — enter something like 6.5 for a six-and-a-half-hour shift or 7.75 for seven hours forty-five minutes. The calculator accepts fractional hours directly rather than requiring separate hour and minute fields for the shift length.
What if my shift has more than one break?
Add the break minutes together and enter the combined total in the single break field — a 15-minute break plus a 30-minute lunch is 45 minutes total unpaid time for this calculation.
Does this account for paid breaks?
No — it assumes the entered break minutes are unpaid time added onto the shift length you enter, which should already reflect your paid working hours. If your break is paid, don't add it separately; just fold it into your shift length instead.