How should unpaid lunch breaks be handled when calculating hours worked?

Subtract the break duration from the total clocked time after calculating the raw clock-in-to-clock-out span, so an 8-hour shift with a 30-minute unpaid lunch shows as 7.5 paid hours, not 8.

What happens if an employee forgets to clock out?

Without a clock-out timestamp there's no way to calculate a duration mathematically; most systems flag the entry as incomplete and require a manager to enter a correction manually rather than guessing at an end time.

Can this method handle a shift that runs more than 24 hours?

A simple clock-in/clock-out pair assumes a shift crosses midnight at most once; shifts genuinely longer than 24 hours need explicit start and end dates as well as times, not just times of day, to calculate correctly.

How to Calculate Hours Worked From Clock-In and Clock-Out Times (Including Overnight Shifts)

Calculating hours worked from a clock-in and clock-out time looks trivial for a normal daytime shift, just subtract the earlier time from the later one, but that same simple subtraction silently breaks for any shift that crosses midnight. Since payroll and scheduling systems both rely on getting this number exactly right, it's worth understanding why the overnight case needs different handling.

The straightforward case

For a same-day shift, say clock-in at 9:00 AM and clock-out at 5:30 PM, converting both times to minutes since midnight (540 and 1050 respectively) and subtracting gives 510 minutes, or 8.5 hours. This works fine as long as the clock-out time is later in the day than the clock-in time, which covers the majority of shifts but not all of them.

Why overnight shifts break simple subtraction

A shift that starts at 10:00 PM and ends at 6:00 AM the next morning is a real 8-hour shift, but converting both to minutes since midnight gives 1320 for the clock-in and 360 for the clock-out. Subtracting the smaller from the larger the naive way (360 minus 1320) produces a negative number, which is obviously wrong for a duration. The fix is to detect that the clock-out time is numerically earlier than the clock-in time, treat that as a signal the shift crossed midnight, and add 24 hours (1440 minutes) to the clock-out value before subtracting, giving the correct 480 minutes, or 8 hours.

This overnight case is one of the most common bugs in hand-rolled timesheet spreadsheets, since a formula that works perfectly for every daytime entry will silently return a negative or nonsensical number the first time someone enters a night-shift pair. The Hours Worked Calculator detects and handles the overnight case automatically, so you don't need a separate formula for night shifts.

Unpaid breaks and rounding

Once you have the raw duration, most workplaces subtract unpaid break time (a 30-minute or 60-minute lunch, for example) to get paid hours, and some also round the clock-in/clock-out times themselves to the nearest interval before calculating, a practice covered in detail in our guide on time card rounding rules. If you need the duration between two arbitrary timestamps rather than a work shift specifically, the general-purpose Time Duration Calculator handles that broader case.