What is a workweek?

Overtime is counted per workweek, not per calendar week or pay period. What the legal workweek is and why its start day matters.

Last reviewed September 23, 2026 by Time Card Calculator Tool

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Every overtime calculation starts with a question most people never ask: which seven days count as the week? The answer is the workweek, and it does not have to be Monday to Sunday, or the same as the pay period.

The definition

Under 29 CFR 778.105, an employee's workweek is a fixed and regularly recurring period of 168 hours, seven consecutive 24 hour periods. It can begin on any day of the week and at any hour of the day. Once set, it stays fixed. It can be changed only if the change is meant to be permanent and is not designed to avoid paying overtime.

Why it matters for overtime

The Fair Labor Standards Act requires overtime for hours over 40 in each workweek, taken on its own. Two rules follow from that:

• No averaging. A 50 hour week followed by a 30 hour week is 10 hours of overtime, even though the two week total is 80. The employer cannot average them to 40.
• The start day changes the answer. The same seven shifts can produce overtime or not, depending on where the workweek boundary falls.

Example: same shifts, different workweek

A worker does 10 hour shifts on Thursday, Friday, Saturday, Sunday and Monday, and nothing else for a fortnight. If the workweek runs Sunday to Saturday, week one has Thursday to Saturday (30 hours) and week two has Sunday and Monday (20 hours): no overtime. If it runs Thursday to Wednesday, all five shifts fall in one week (50 hours): 10 hours of overtime. Neither is wrong, as long as the workweek was set in advance and not moved to dodge the overtime.

Workweek versus pay period

The pay period is when you get paid. The workweek is how overtime is counted. On a weekly or biweekly schedule they usually line up. On a semi-monthly or monthly schedule they do not, and a single workweek can be split between two pay periods. Overtime is still worked out for the whole workweek; see biweekly vs semi-monthly pay.

Workweek versus workday

Federal law has no daily overtime, so the workday only matters in states that do. In those states the workday is usually a consecutive 24 hour period that also starts at a fixed time. California's seventh day rule depends on the workweek: it applies only when all seven days of a single workweek are worked. See states with daily overtime.

Finding your workweek

Your employer should be able to tell you when the workweek starts, and it is often printed in the handbook or on the time clock report. When you total hours with the time card calculator, set "workweek starts on" to the same day so the weekly overtime split matches payroll.