Schedule comparison

24/48 vs Kelly Schedule: Do Kelly Days Really Cut Your Hours?

A pure 9-day Kelly rotation averages the same 56 hours a week as a 24/48, not fewer. Only a recurring Kelly day layered on top actually cuts your hours.

The baseline24/48One 24 on, two off, repeating every three days.
vs
Same hours9-day KellyThree 24s across nine days, days off clustered.
~56 hAvg work weekidentical~56 h
3 daysCycle length9 days
~121Shifts / yearidentical~121
~224 hHours / 28 daysidentical~224 h
~12 hOvertime / 28 daysidentical~12 h
spread 2 at a timeDays offclustered

Add a recurring Kelly day on top of the 24/48 and the average drops to ~50 to 51 h a week. That added day off is the only thing that cuts hours, not the nine-day cycle.

An estimate for planning, not legal or payroll advice. FLSA 7(k) thresholds follow 29 CFR 553.230 (fire protection). Your contract and declared work period may differ.

Key differences

What actually changes between them

The nine-day myth

Three 24-hour shifts over nine days is 72 hours divided by 9, times 7, which is exactly 56.0 hours a week. Any comparison quoting a 9-day cycle at 53 hours has the arithmetic wrong, and your paycheck will not match it.

What a Kelly day really is

Not a rotation. A Kelly day is an EXTRA recurring day off layered on a 24/48, scheduled every few tours to pull the average below the FLSA 7(k) cap. That added day off is the only thing that removes hours.

The real reduction

Drop one 24-hour shift on a recurring cadence and a 24/48 lands near 50 to 51 hours a week, and the 28-day period falls from about 224 hours toward or under the 212-hour cap. Frequency is the lever.

The overtime effect

A straight 24/48 and a pure 9-day cycle both carry roughly 12 built-in overtime hours a period. A recurring Kelly day can trim or eliminate it; clustering days off does not.

The coverage trade

Every Kelly day is one fewer body on the floor that day, so the department backfills or accepts a lighter roster. That is why the honest number matters: you cannot weigh coverage against hours saved that were never real.

The context

Clustering days off is not the same as removing hours

You will see it repeated everywhere: a 9-day Kelly rotation is lighter than a 24/48, often quoted around 53 hours a week. It is not. A pure nine-day cycle is three 24-hour shifts spread across nine days, which works out to exactly 56.0 hours a week, the same average as a straight 24/48. The nine-day version only changes where your time off lands, clustering it into a longer break instead of spreading it two days at a time.

A real Kelly day is different. It is an extra recurring day off, layered on top of a 24/48, that a department schedules every few tours specifically to pull the average work week below the FLSA 7(k) overtime cap of 212 hours per 28-day period. Removing that one scheduled 24-hour shift is the only thing that actually reduces hours, dragging a 24/48 down toward 50 or 51 hours a week and the period under the cap.

So if your goal is to control overtime rather than just rearrange your days off, the Kelly day is the tool, not the nine-day cycle. Build the 24/48 baseline, then turn on a Kelly day at your contract's real cadence and watch the average and the FLSA 7(k) position move to your true numbers.

Common questions

Questions firefighters ask

Does a Kelly schedule have fewer hours than a 24/48?

Not the 9-day version. A pure 9-day Kelly rotation is three 24-hour shifts over nine days, which is 72 hours divided by 9, times 7, or exactly 56.0 hours a week, the same as a 24/48. It only clusters your days off into a longer break. Hours drop only when a department adds a recurring Kelly day that removes a scheduled shift.

What is a Kelly day exactly?

A Kelly day is an extra recurring day off layered on top of a 24/48, scheduled every few tours to pull the average work week below the FLSA 7(k) overtime cap. It is not the name of a nine-day rotation. The Kelly day is the added day off, and removing that one scheduled 24-hour shift is what actually lowers your hours.

How much does a Kelly day reduce my hours?

It depends on how often the Kelly day recurs. A straight 24/48 averages about 56 hours a week; adding a regular Kelly day typically brings that down toward 50 to 51 hours, and drops the 28-day period from about 224 hours toward or under the 212-hour cap. The more frequent the Kelly day, the lower the average. The calculator computes your exact number from your cadence.

Does a Kelly day reduce overtime?

Only if it pushes your scheduled hours under the cap. A straight 24/48 runs about 224 hours in a 28-day period against the FLSA 7(k) fire cap of 212, so roughly 12 hours of overtime are built in. A recurring Kelly day can pull the period down to the cap or below it, trimming or eliminating that built-in overtime. A pure 9-day rotation still averages 224 hours, so it carries the same built-in overtime.

Why is it called a Kelly day?

The name traces to a Chicago fire commissioner, Edward J. Kelly, credited with the practice of granting firefighters a recurring extra day off to keep average hours in check. The label stuck, and today Kelly day is the standard term across US fire departments for that scheduled recurring day off built into a rotation.

How do I calculate my real average work week?

Use the Kelly day calculator. It starts at the honest 56-hour 24/48 baseline, then lets you turn on a Kelly day and set your contract's actual cadence. It recomputes your true average work week and your FLSA 7(k) work-period position in real time, and projects your exact on-duty days for the next 24 months.

Build either one

See it on a real calendar before you commit

Model either rotation free, no signup, and watch the days off, recovery blocks, and hours fall on an actual month.

Build the 24/48One 24 on, two off, repeating every three days.Build the 9-day KellyThree 24s across nine days, days off clustered.
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