Source: https://clockwage44.com/tools/workweek-start-day-overtime-calculator/

ClockWage44 is a free hours and pay tracker app for iOS and Android: log shifts across every job and see take-home pay after federal tax, state tax, FICA, overtime and deductions.

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# Workweek Start Day Overtime Calculator

See how many overtime hours a shift rotation earns under all seven FLSA workweek start days, plus the yearly pay gap between the best and worst.

_Interactive tool: open [the web page](https://clockwage44.com/tools/workweek-start-day-overtime-calculator/) to use it. This Markdown copy has the text only._

A rotation only reacts to the workweek start day when its cycle is a whole number of weeks: 7, 14, 21, or 28 days.

Your workweek start day is whatever your employer declared in writing. It is often in the handbook or on the posted schedule policy, and it is frequently not the day your pay period starts.

Drop this below 52 if you take unpaid weeks off. Per-week figures do not change, annual figures scale with it.

One flat rate, no 50-state engine. Leave it at 0 if you do not want state tax in the estimate.

Every dollar of the start-day gap is FLSA half-time premium, which is exactly the qualified overtime compensation the IRC 225 deduction covers.

Average hours per week is identical for every start day. Moving the cut never changes how many hours you work, only how many of them are paid at the premium.

Take-home is a marginal-rate estimate, not a withholding calculation.

Your current start day is highlighted. Hours worked are identical in every row, so the whole difference is the half-time premium on hours over 40.

Estimates only. This is not tax or legal advice. Check your state's rules and your employer's written workweek policy.

## Your workweek start day is a real number on your paycheck

Take a 2-2-3 rotation on 12-hour shifts, the schedule most 24/7 plants, hospitals, and dispatch centers run. Two on, two off, three on, two off, two on, three off. Over the 14-day cycle you work seven shifts, 84 hours, 42 hours a week on average. That much is fixed.

Now cut it into workweeks. If your employer's workweek starts Monday and your rotation's first ON day is a Monday, week one holds five shifts (60 hours) and week two holds two (24 hours). That is 20 overtime hours every two weeks, 520 a year. Shift the declared start day to Sunday and the same seven shifts split four and three: 48 hours and 36 hours, 8 overtime hours every two weeks, 208 a year.

Same shifts. Same 84 hours. Same rotation. At $25 an hour the difference is $3,900 a year, and every cent of it is the half-time premium, because the total hours never move. Only the count of hours sitting above 40 in a 168-hour bucket does.

29 CFR 778.105 defines that bucket: a workweek is a fixed and regularly recurring period of 168 hours, seven consecutive 24-hour periods. It can start on any day of the week and at any hour of the day. It does not have to line up with the calendar week, and it does not have to line up with your pay period. Most workers have never been told which day theirs starts.

## When the start day matters, and when it can't

Here is the part no other calculator will tell you: on most rotations, the start day makes no difference at all over a full year. Whether it matters comes down to one question. Does your cycle repeat on a whole number of weeks?

A pattern of length L lines up against the 7-day workweek on a repeat of lcm(L, 7) days. When L shares no factor with 7 (8-day, 9-day, 10-day cycles), moving the cut by one day just rotates the same set of workweeks into a different order. The multiset is identical, so the annual total is identical. When L is 7, 14, 21, or 28, the alignments are genuinely different schedules, and the spread can be enormous.

| Pattern | Cycle | Avg hrs/wk | OT hrs/yr range |
| - | - | - | - |
| 2-2-3 (Pitman), 12h | 14 days | 42.0 | 208 to 520 |
| DuPont, 12h | 28 days | 42.0 | 208 to 624 |
| 7 on / 7 off, 12h | 14 days | 42.0 | 208 to 1,144 |
| 4 on / 4 off, 12h | 8 days | 42.0 | 208 flat |
| 6 on / 2 off, 8h | 8 days | 42.0 | 104 flat |
| 5 on / 2 off, 8h | 7 days | 40.0 | 0 |

Every one of those rotations averages 42 hours a week except the last, so they all look equivalent on a schedule-generator page. They are not. 7-on-7-off at 12 hours swings by 936 overtime hours a year, worth $11,700 at $25 an hour, purely on where the cut falls. 4-on-4-off swings by nothing, because an 8-day cycle drifts across the calendar and each start day eventually covers the same mix of heavy and light weeks.

A standard 5x8 sits at the other end. Its cycle is exactly 7 days, so every 168-hour window contains the entire cycle and every workweek holds exactly 40 hours no matter where you cut it. There is no weekly overtime to move around.

## What your employer is and isn't allowed to do

The workweek is the employer's to declare, and the choice is legitimate. 29 CFR 778.105 lets an employer set one workweek for the whole establishment or different workweeks for different groups. What it does not allow is treating the boundary as a dial. A change to the beginning of the workweek is permitted only "if the change is intended to be permanent and is not designed to evade the overtime requirements of the Act." A start day that moves whenever a big week is coming fails both halves of that test.

29 CFR Part 778 Subpart D covers the changeover itself. When a permanent change creates an overlap week, the employer generally computes that week under both the old and the new boundary and pays whichever produces more.

The other rule worth knowing is 29 CFR 778.104: each workweek stands alone. The Act "does not permit averaging of hours over 2 or more weeks." Thirty hours one week and 50 the next is 10 overtime hours, not two tidy 40s. Being paid biweekly does not merge the two, because the pay period and the workweek are separate structures. The one narrow exception is the 8-and-80 rule for hospitals and residential care facilities under 29 USC 207(j), which needs a written agreement with the employee.

Practically: find out which day yours starts. It should be documented somewhere, in the handbook, the schedule policy, or your offer letter. Ask HR if it is not. You cannot check your overtime without it.

## Prove it with your own shifts

A rotation on paper is clean. Your actual year is not. You pick up a shift, someone swaps out, a holiday lands mid-cycle, and by March the neat 14-day pattern this page models has stopped matching what you worked.

[ClockWage44](https://clockwage44.com/#download) tracks the real version: actual clock-in and clock-out times per shift, against a workweek start day you set per job. The weekly overtime rule runs on whatever hours truly landed inside each 168-hour window, and federal tax, state tax, FICA, and deductions come off that on-device to leave a take-home figure. Log every shift, then hold your pay stub next to what the workweek boundary says you are owed.

## Frequently Asked Questions

Common questions about workweek start day overtime calculator

### What is an FLSA "workweek"?

Under 29 CFR 778.105, a workweek is "a fixed and regularly recurring period of 168 hours, seven consecutive 24-hour periods." It does not have to match the calendar week. It can start on any day and at any hour, as long as it stays fixed. An employer can set one workweek for the whole establishment, or different workweeks for different groups of employees. That declared start day is the only thing this calculator changes.

### Can my employer change the day my workweek starts?

Yes, but with a limit. 29 CFR 778.105 permits changing the beginning of the workweek "if the change is intended to be permanent and is not designed to evade the overtime requirements of the Act." A change made to shave overtime off a rotation, or one that keeps flipping back and forth, is not a lawful permanent change. 29 CFR Part 778 Subpart D also covers the transition week: the employer generally computes the overlap week both ways and pays the greater amount.

### Why did my overtime drop when my schedule didn't change?

Because overtime is counted per workweek, not per shift or per pay period. Move the cut and the same shifts fall into different 168-hour buckets. On a 2-2-3 rotation with 12-hour shifts, a Monday workweek produces alternating 60-hour and 24-hour weeks, which is 20 overtime hours every two weeks. A Sunday workweek turns the same shifts into 36-hour and 48-hour weeks, or 8 overtime hours every two weeks. Same 84 hours worked either way: 520 overtime hours a year versus 208. The [overtime calculator](https://clockwage44.com/tools/overtime-calculator/) handles the single-week version of that math.

### Is it legal to average two weeks together to avoid overtime?

No, not for a typical employer. 29 CFR 778.104 says the Act "takes a single workweek as its standard and does not permit averaging of hours over 2 or more weeks." Each workweek stands alone. 30 hours one week and 50 the next means 10 overtime hours, and it cannot be called 40 and 40. Paying biweekly does not change this, because the pay period and the workweek are separate things (see the [pay period calculator](https://clockwage44.com/tools/pay-period-calculator/)). The narrow exception is the "8 and 80" rule for hospitals and residential care facilities under 29 USC 207(j), which requires a written agreement with the employee.

### Does the start day matter on a 4-on-4-off rotation?

Over a full year, no. A 4-on-4-off cycle is 8 days long, so it drifts across the calendar and every start day ends up covering the same mix of heavy and light weeks, about 208 overtime hours a year either way. The start day only moves your annual total when the rotation repeats on a whole number of weeks: 7, 14, 21, or 28 days. That is why 2-2-3, 7-on-7-off, and DuPont are so sensitive to it and 4-on-4-off is not.

### Does a 2-2-3 schedule always generate overtime?

At 12-hour shifts, yes. It averages 42 hours a week, so some workweek is always over 40. How much overtime depends entirely on the cut: 208 hours a year at the low end, 520 at the high end, on identical shifts. At 8-hour shifts the same rotation averages 28 hours a week and never crosses 40, so no weekly overtime arises at all. Switch the shift length above to see both cases.

### My pay period is biweekly, does that change anything?

No. Overtime is owed per workweek even when you are paid every other week. A biweekly pay period contains two separate workweeks and each is evaluated on its own. What matters for your overtime is the declared workweek start day, not the pay date. The [pay period calculator](https://clockwage44.com/tools/pay-period-calculator/) maps pay dates to workweeks if the two are out of step.

### What about daily overtime and state rules?

This calculator models the federal weekly rule only: hours over 40 in a workweek at 1.5x. Several states add daily overtime (over 8 or over 12 hours in a day), seventh-consecutive-day rules, or double time, and those can produce overtime the weekly test alone misses. On a 12-hour rotation in a daily-overtime state, the start day matters much less, because the daily rule is already capturing the long shifts. Check your state's rules, or use the [double time calculator](https://clockwage44.com/tools/double-time-calculator/) and the [time and a half calculator](https://clockwage44.com/tools/time-and-a-half-calculator/).

## Related Tools

- [12 Hour Shift Pay Calculator](https://clockwage44.com/tools/12-hour-shift-pay-calculator/): Calculate 12 hour shift pay for 2-2-3, DuPont, and 4-on-4-off rotations. Get true per-week overtime, gross pay, and an estimated take-home figure.
- [Blended Overtime Calculator](https://clockwage44.com/tools/blended-overtime-calculator/): Enter the hours and pay rate for each job you work in a week to get the FLSA weighted-average regular rate and the blended overtime pay you're owed.
- [Double Time Pay Calculator](https://clockwage44.com/tools/double-time-calculator/): Calculate double time pay at 2x your hourly rate, with time-and-a-half and regular pay. Includes a California mode for the over-12 and 7th-day rules.
- [Holiday Pay Calculator](https://clockwage44.com/tools/holiday-pay-calculator/): Enter your hourly rate, holiday hours, and premium multiplier to see holiday pay, regular pay, and total gross in seconds.