How 4/10, 9/80 and 3/12 work schedules add up

Updated November 15, 2026 · Worked examples use whole minutes

A compressed schedule fits full-time hours into fewer, longer days. A 4/10 is four 10-hour days, or 40 hours a week. A 9/80 is 80 hours over nine working days in two weeks, with a day off. A 3/12 is three 12-hour shifts, or 36 hours a week, common in hospitals.

Calculate it step by step

Write the start and finish of each working day, including the unpaid break.
Calculate each day’s worked hours: finish minus start, minus the unpaid break.
Add the days in each workweek separately.
For a 9/80, check the two weeks against your employer’s workweek boundary rather than calendar weeks.

Worked example

A 4/10 from 7:00 am to 5:30 pm with a 30-minute unpaid lunch gives 10 hours a day and 40 hours a week. A 3/12 from 7:00 am to 7:30 pm with a 30-minute unpaid break gives 12 hours a shift and 36 hours a week.

A 4/10 fits the same 40 hours as a 5/8 into four days, and a 3/12 is 36 hours. A 9/80, not drawn, works 44 and 36 hours in its two calendar weeks, which is why employers often move the workweek boundary.

Check your own shifts in the time card calculator

Hours on common compressed schedules

Hours on common compressed schedules
Schedule	Working days	Hours a day	Hours a week
5/8 (standard)	5 a week	8	40
4/10	4 a week	10	40
9/80	9 in two weeks	9, plus one 8-hour day	80 per two weeks
3/12	3 a week	12	36

How do these schedules interact with overtime?

Clock times include unpaid breaks. Ten worked hours with a 30-minute unpaid lunch need a 10-hour-30-minute span, such as 7:00 am to 5:30 pm. A 9/80 usually has eight 9-hour days and one 8-hour day.

Under US federal law, overtime depends on hours over 40 in a workweek, so a 4/10 normally has none. For a 9/80, employers often start the workweek partway through the 8-hour day so each workweek totals 40. States with daily overtime, such as California, treat long days differently unless an approved alternative workweek schedule is in place.

Quick answers

What is a 9/80 work schedule?

Eighty hours worked over nine days in a two-week period, usually eight 9-hour days and one 8-hour day, giving one extra day off every two weeks.

Is a 4/10 schedule 40 hours?

Yes. Four 10-hour days total 40 worked hours a week, not counting unpaid breaks.