If you run a plant, a control room, or any operation that never turns the lights off, sooner or later someone hands you a grid of letters and asks you to make sense of it. The DuPont schedule is one of the oldest and most recognizable of those grids: a 4-crew, 12-hour-shift rotation that covers a facility 24 hours a day, 7 days a week, and famously gives every worker one full stretch of seven days off in each four-week cycle. It came out of the DuPont chemical company decades ago, and it is still in heavy use in manufacturing, refining, utilities, and emergency services today.
This post explains what a DuPont schedule actually is, walks through a concrete DuPont schedule example week by week, covers the “modified DuPont schedule” variants people ask about, and touches on the health question that shows up in every search for this topic. At the end I will point you at a free tool where you can build one yourself.
Download the DuPont schedule template (.xlsx) — free, editable, no signup. Or skip the static grid and build your real schedule at staff-scheduling.kindoflost.com.
What is a DuPont schedule?
A DuPont shift schedule splits your workforce into four crews, usually labeled A, B, C, and D. Each crew works 12-hour shifts and rotates through the same fixed sequence of days, nights, and rest, just offset from the other crews by a week. At any given moment two crews are working — one on the day shift, one on the night shift — and the other two are off. Rotate all four crews through the pattern and you get continuous round-the-clock coverage with no gaps.
The whole thing repeats on a 28-day cycle. Over those four weeks, a single crew works 14 twelve-hour shifts, which comes to 168 hours, or an average of 42 hours per week. That “42 average” is the number most sources quote, and it is worth remembering because those hours do not arrive evenly — more on that in a moment.
A DuPont schedule example, week by week
The DuPont work schedule is most commonly described as a single 28-day sequence that each crew marches through. Using D for a 12-hour day shift, N for a 12-hour night shift, and a dash for a day off, one crew’s four weeks commonly look like this:
- Week 1: four night shifts, then three days off —
N N N N - - - - Week 2: three day shifts, one day off, then three night shifts —
D D D - N N N - Week 3: three days off, then four day shifts —
- - - D D D D - Week 4: seven days off —
- - - - - - -
Add up the letters and you get 14 shifts: four nights, three days, three nights, four days. The other three crews run the exact same sequence, each starting a week later, so that on any calendar day one crew is on days, one is on nights, and two are resting. The signature feature is obvious in Week 4 — a genuine seven-day break, which is the main reason workers on 24/7 operations tend to like this pattern.
One honest caveat: sources differ on small details, such as whether the cycle is written starting on days or on nights, and how the rest days are grouped between blocks. The count that everyone agrees on is 14 twelve-hour shifts per crew over 28 days and the seven-day break. So treat the grid above as the common form of the DuPont schedule rather than the one and only legal version — the exact letter-by-letter layout your facility uses may be rotated or mirrored.
Why the hours feel “lumpy”
The 42-hour weekly average hides a lot of variation. Because the shifts are bunched, a crew’s actual hours swing week to week — some weeks land around 36 or 48 hours, and the heaviest block in the cycle can stack up well past a standard 40-hour week before the seven days off arrive. In the United States, overtime under the Fair Labor Standards Act is generally triggered by hours worked in a single week, so this uneven distribution matters for payroll: the overtime premium tends to concentrate in the crew’s heavy weeks. If you are costing out a DuPont rotation, average weekly hours alone will mislead you — you have to look at the week-by-week distribution.
The modified DuPont schedule
“Modified DuPont schedule” is a catch-all for the tweaks operations make once they live with the standard pattern for a while. There is no single official modified version, but the common goals are to smooth out the heavy week, close the gap where no senior crew is on site, or cover predictable absences. Typical adjustments include adding a fifth crew to bring average weekly hours down, converting one 12-hour block into a shorter shift, or inserting a training or handover shift. Each of these changes the hours math and the coverage, so if you adopt one, re-check both the overtime exposure and whether you still have the right skills on every shift.
Is the DuPont schedule bad for your health?
This is one of the most common searches on the topic, so it is worth addressing plainly rather than dodging. The concern is real but general, and it is not unique to DuPont — it applies to any pattern built on 12-hour shifts and night work. The U.S. National Institute for Occupational Safety and Health (NIOSH) reviewed the research on long and extended shifts and reported associations with increased fatigue and a higher risk of errors and injuries as shift length and consecutive hours rise. You can read their summary in Overtime and Extended Work Shifts: Recent Findings. The takeaway is not “12-hour rotations are dangerous, avoid them” — plenty of well-run 24/7 operations use them safely — but that shift length, night work, and rest between shifts are worth designing deliberately rather than by accident. The DuPont pattern’s built-in seven-day break and its rule of a rest day between night and day transitions are partly a response to exactly these concerns.
Build a DuPont rotation yourself
Understanding the pattern on paper is one thing; laying it out across four named crews on real calendar dates, then checking coverage and hours, is where it gets fiddly. That is the kind of problem I have spent 20-plus years solving in Excel, and lately I have been turning those models into free web apps. The scheduling engine behind this started as a one-client shift model and grew into a general tool — I wrote about that journey in going from one client’s rules to any team.
If you want to see a DuPont schedule assembled with your own crew names and start date — and check the coverage and the lumpy hours for yourself — you can do it free, no signup, at staff-scheduling.kindoflost.com. Type your data in, paste it from Excel, or import a workbook, and let the tool lay out the rotation. It is a genuinely useful way to pressure-test a DuPont pattern before you commit a real team to it.
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