How to Calculate Work Hours With an Unpaid Lunch Break

To calculate paid work hours, find the time between the start and end of the shift, then subtract only the break time that is unpaid. The basic arithmetic is simple, but overnight shifts, decimal-hour payroll systems, and break rules can make a time card confusing.

The Ziannah Work Hours Calculator handles the time arithmetic. This guide explains the formula, shows common examples, and separates the calculation from the employment rules that determine whether a break should actually be unpaid.

The work-hours formula

Paid work time = shift end time - shift start time - unpaid break time.

Example: a shift starts at 9:00 AM and ends at 5:30 PM. The elapsed shift is 8 hours 30 minutes. Subtract a 30-minute unpaid lunch and the paid result is 8 hours, or 8.0 decimal hours.

Calculate the shift step by step

• Write the start and end times using the same 12-hour or 24-hour format.
• Find the total elapsed time between those two times.
• Subtract the minutes for any break that is correctly treated as unpaid.
• Convert the remaining minutes to a decimal if your time card or payroll system requires it.

When should a lunch break be subtracted?

Under general federal guidance from the U.S. Department of Labor, short rest periods of about 20 minutes or less are usually counted as paid working time. A bona fide meal period, typically 30 minutes or more, generally does not need to be paid when the employee is completely relieved from duty.

A meal period is not automatically unpaid just because it appears on a schedule. If an employee must continue handling calls, serving customers, monitoring equipment, or performing another duty while eating, the time may still count as hours worked under federal guidance.

State and local requirements can be different or more protective. Use this calculator for arithmetic, and confirm the break treatment that applies to the employee, workplace, and location.

How to calculate an overnight shift

When the end time is earlier than the start time, treat the end as occurring on the following day. A shift from 10:00 PM to 6:00 AM is eight elapsed hours. After a 30-minute unpaid break, the paid time is 7 hours 30 minutes.

Convert minutes to decimal hours

Divide minutes by 60 to get the decimal part of an hour. Fifteen minutes is 0.25 hours, 30 minutes is 0.5 hours, and 45 minutes is 0.75 hours. Therefore, 7 hours 30 minutes becomes 7.5 decimal hours.

Common time-card mistakes

• Writing 7 hours 30 minutes as 7.30 hours. In decimal time, it is 7.5 hours.
• Subtracting a short paid rest break as though it were an unpaid meal period.
• Forgetting that an end time after midnight belongs to the following day.
• Rounding each shift differently instead of following one consistent timekeeping policy.

Calculate one shift or a full week

Use the Work Hours Calculator for one shift. Use the Time Card Calculator when you need to add several days, compare the total with an overtime threshold, and estimate gross pay.