Does my employer stack shift differentials or pay the highest single?

It depends on the pay policy — which is usually in the employee handbook, not the offer letter. Stacking employers (common in California, union-contract facilities, Magnet hospitals) pay every applicable differential on every hour: a night-weekend-holiday shift pays base + night + weekend + holiday on every worked hour. Highest-single employers (common in Southern states and some for-profit systems) pay only the largest applicable differential for each hour. The delta for a nurse working 3×12 night-weekend shifts is typically $150-$400/week. Ask HR for the pay-code matrix before signing.

What does California Labor Code § 510 mean for my 3×12 schedule?

California requires 1.5× the regular rate for hours 8-12 in a workday and 2× for hours beyond 12. A 12-hour shift in CA pays 8 hours at straight-time plus 4 hours at time-and-a-half — meaning every 12-hour shift has 4 hours of built-in daily overtime. Three 12s per week add up to 36 total hours (below the 40-hour weekly OT threshold) but produce 12 hours of daily OT per week. On the 7th consecutive day of work in a workweek, the first 8 hours are OT and hours beyond 8 are double-time. California is the only state where a standard 3×12 schedule generates significant OT premium at 36 hours/week.

Why did my big paycheck this pay period get taxed so heavily?

IRS Publication 15 allows employers to withhold on supplemental wages (bonuses, differentials, holiday pay) using either (1) the flat 22% supplemental rate or (2) the aggregate method, which adds the supplemental amount to regular wages and withholds at the employee's marginal W-4 rate. For an RN at $95K taxable income, the flat 22% method typically over-withholds by $50-$250 per pay period compared to aggregate — money you get back at tax time but not when you need it. If your paychecks with heavy differentials feel disproportionately reduced, ask payroll which method they use and whether they can switch to aggregate. You'll still owe the same annual tax; the timing of withholding is what changes.

How does Colorado COMPS Order #39 treat 12-hour shifts?

Colorado's COMPS Order #39 (7 CCR 1103-1, effective 2024-01-01) requires 1.5× after 12 hours worked in a workday, 12 consecutive hours regardless of workday boundary, or 40 hours per workweek — whichever produces greater pay. A standard 12-hour shift sits exactly at the threshold: no daily overtime is triggered unless the shift runs past 12 hours (overtime, stayed-late, mandatory hold). This is materially different from California's 8-hour daily threshold, which does trigger 4 hours of daily OT on every 12-hour shift.

Does Kentucky really give overtime on the 7th consecutive day?

Yes. Kentucky Revised Statute 337.050 requires 1.5× the regular rate for all hours worked on the 7th consecutive day of work within a workweek. Hospitals with self-scheduling or 3×12 schedules that break up consecutive blocks avoid this premium structurally. If your schedule regularly includes seven straight workdays (either by policy or voluntary pickup), you're entitled to OT on the 7th day — even if your weekly total is below 40 hours overall, the 7th-day hours still trigger the premium.

What is Illinois's One Day Rest In Seven Act?

820 ILCS 140 (amended 2023) requires every employee to receive 24 consecutive hours of rest in every 7-consecutive-day period, plus a 20-minute meal period for every 7.5-hour shift worked, plus an additional 20-minute meal for shifts over 12 hours. It's not an overtime premium but a scheduling constraint. Employer violations are $250-$500 per employee per offense, enforceable through the Illinois Department of Labor. If your hospital schedules you 14 consecutive days without 24 hours of rest, that's a reportable violation — separate from any overtime claim.

Does overtime pay count the differentials in the regular rate?

Under FLSA, yes — but in practice many employers compute OT only on base hourly. The FLSA 'regular rate' for overtime includes non-discretionary bonuses and shift differentials. A nurse earning $45 base + $5 night differential should theoretically receive 1.5× the blended $50 rate for OT hours worked at night. Some employers compute this correctly; others pay OT at 1.5× base only, shorting the differential portion. This calculator shows OT premium on base only for simplicity; the true FLSA-compliant rate is higher. If you work significant OT-on-differential hours, audit your paystub — DOL Wage and Hour Division investigates blended-rate miscalculation claims.

Is this legal advice?

No. This calculator cites published state overtime statutes and IRS Publication 15 withholding rules. Your employer's specific pay policy, any collective bargaining agreement, alternative workweek schedule (AWS) election, or employment contract language may produce different numbers. Before disputing a paycheck calculation, consult your HR pay-policy handbook or a nurse-employment attorney in your state.

Nursing Shift Differential Calculator

Weekly gross math for working RNs: base hourly + stacked (or highest-single) night / weekend / holiday / charge / preceptor differentials, state-aware daily overtime (California 8-hr, Colorado 12-hr, Alaska 8-hr, Nevada 8-hr, Kentucky 7th-consecutive-day, Illinois scheduling), and the IRS Publication 15 supplemental-vs-aggregate withholding reality on differential-heavy paychecks.

Last verified 2026-04-21 Primary sources: FLSA 29 USC §207 · CA Labor Code §510 · IRS Pub 15

Published state OT law + standard interpretation — not legal advice. Your employer's pay policy or a collective-bargaining agreement may apply different rules. Consult HR pay-policy documents or a nurse-employment attorney before disputing a calculation.

Run your weekly gross math

Base + schedule

Base hourly ($/hr) Hours per shift Day-weekday hours/week Night-weekday hours/week Day-weekend hours/week Night-weekend hours/week

Differential rates ($/hr)

Night differential Weekend differential Holiday differential Charge-nurse differential Preceptor differential Charge hours/week Preceptor hours/week Holiday shifts/year

Typical: 3 (every 3rd holiday rotation). Amortized to weekly premium.

Policy + state

Stacking policy

Check your employee handbook or collective-bargaining agreement. Southern / non-union facilities often pay highest-single; Magnet / union / California systems often stack.

State OT rule

Weeks worked per year

Typical 48 (4 weeks PTO/holidays off). Use 52 for travel nurse without breaks.

Marginal federal tax rate

Effective blended hourly
Total hours/week
Annualized gross
Weekly breakdown
Base pay
Night premium
Weekend premium
Holiday premium (amortized)
Charge premium
Preceptor premium
OT premium (½ × base)
DT premium (1× × base)
Stack vs highest-single delta
State OT rule applied
Daily OT hours/week
Daily DT hours/week
Weekly OT hours
IRS withholding on differentials
Supplemental flat (22%)
Aggregate method (estimate)
Flat vs aggregate delta

Why this calculator exists

Every shift an RN works has a differential math question behind it. Night + weekend + holiday at a stacking Magnet hospital pays materially more than the same shift at a highest-single Southern system. A 3×12 in California triggers daily overtime that a nurse in the same schedule in Texas never sees. A paycheck that stacks five differentials can trigger the IRS 22% supplemental withholding rate, producing a take-home number $200 lower than the aggregate-method would calculate.

None of that is visible on the offer letter. It's in the pay-policy handbook, the state statute, and IRS Publication 15. This calculator surfaces all three on one screen so nurses running real schedules can see real numbers.

Stacking vs highest-single — the single most valuable question to ask HR

Two nurses with identical schedules, identical base rates, identical differential rates can earn hundreds of dollars per week apart based on their employer's stacking policy. The policy is set by HR pay-code configuration in Workday / Lawson / UKG, and the difference is usually:

Stack: Every applicable differential applies to every worked hour. Night-weekend-holiday shift = base + night + weekend + holiday on all 12 hours. Common in: California state systems, Magnet-designated hospitals, union-contract facilities (SEIU, NYSNA, MNA), and many academic medical centers.
Highest single: Only the largest differential applies to each hour. Night-weekend-holiday shift = base + holiday (since holiday is highest). Common in: Southern for-profit systems (HCA in some markets, Community Health Systems), non-union community hospitals, and some long-term-care.

For a nurse working 3×12s on nights including one weekend shift, stacking vs highest-single typically produces a $100-$250/week delta — $5,000-$12,500 annually. Ask HR for the pay-code matrix before accepting any offer. If they won't provide it in writing, that's information.

State overtime rules that actually affect RN paychecks

State	Rule	Effective on 3×12?	Statute
Federal (FLSA)	1.5× after 40/wk	No (36 < 40)	29 USC §207
California	1.5× after 8/day, 2× after 12/day	Yes (12 hrs OT, 0 DT)	Labor Code §510
Alaska	1.5× after 8/day or 40/wk	Yes (12 hrs daily OT)	AS §23.10.060
Nevada	1.5× after 8/day (waivable) or 40/wk	Depends (AWS waiver common)	NRS §608.018
Colorado	1.5× after 12/day or 12 consecutive or 40/wk	No (shift = 12 exactly)	COMPS Order #39
Kentucky	1.5× on 7th consecutive workday	Depends on pattern	KRS §337.050
Illinois	1.5× after 40/wk + ODRISA scheduling	No (36 < 40)	820 ILCS 140

California is the outlier. A 3×12 nurse in California accrues 12 hours of daily overtime per week — 12 × base × 0.5 premium — on top of stacked differentials. At $55/hr base, that's $330/week of extra OT premium that a Texas or Colorado nurse on the same schedule doesn't receive.

The IRS supplemental-withholding trap

IRS Publication 15 (Circular E) lets employers withhold on supplemental wages — bonuses, differentials, holiday pay, and sometimes PTO cash-out — using one of two methods:

Flat supplemental method: Withhold 22% federal flat on the supplemental portion. Simple for payroll. Over-withholds for most RNs whose marginal rate is below 22% and under-withholds for high-earning nurses whose marginal rate is 24-32%.
Aggregate method: Add supplemental to regular wages for the pay period, withhold at the employee's W-4 marginal rate on the combined total, then subtract what would have been withheld on regular wages alone. Closer to the true marginal rate.

For a nurse in the 24% marginal bracket ($95K-$182K taxable), the flat 22% method under-withholds on differentials — meaning the take-home paycheck is slightly higher than it "should" be, but the nurse owes more at tax time. For a nurse in the 12% marginal bracket ($44K-$95K taxable), the flat 22% method over-withholds — producing a smaller take-home check than aggregate would. This is the most common complaint: "my big holiday paycheck got taxed way harder than my regular one."

Same annual tax owed either way. The timing of the withholding — and therefore the size of each individual paycheck — changes. If you have a cash-flow reason to smooth your paychecks, ask payroll to switch you to aggregate withholding on supplemental.

Our assumptions and sources

Assumption	Source
FLSA weekly OT threshold: 40 hrs	29 U.S.C. § 207(a)(1)
CA 8-hr daily OT + 12-hr DT	California Labor Code § 510 (AB 60, 1999)
AK 8-hr daily OT	Alaska Statute 23.10.060
NV 8-hr daily OT (waivable AWS)	Nevada NRS 608.018
CO 12-hr daily OT	7 CCR 1103-1 (COMPS Order #39), effective 2024-01-01
KY 7th-consecutive-day OT	Kentucky KRS 337.050
IL scheduling constraints	820 ILCS 140 (ODRISA, amended 2023)
Supplemental flat 22% / 37%	IRS Publication 15 (Circular E), 2025
Stacking-vs-highest-single	Standard industry pay-policy variants; verify in your employee handbook
OT premium = base × 0.5 (½ on top of straight)	FLSA 29 CFR § 778.107 — "half-time" method for salaried/fluctuating. For hourly, 1.5× is straight + premium; premium column = 0.5 × base × OT hours.
DT premium = base × 1.0 (full additional)	CA daily-DT construction: DT is straight × 2, premium column = base × DT hours.

Frequently asked questions

My facility is a Magnet hospital. Does that guarantee stacking?

No. Magnet designation is awarded by the ANCC for nursing excellence and shared governance — it does not mandate any specific pay policy. Most Magnet facilities do stack differentials because the culture rewards nurse retention, but this is a correlation not a guarantee. Check your specific pay-code matrix.

I'm a per-diem / PRN RN. Do I still get these differentials?

Usually yes for night/weekend/holiday differentials (they're attached to the shift, not the employment status). Charge and preceptor differentials often are NOT available to PRN — verify in your agreement. State OT rules apply identically; overtime law does not distinguish by employment category.

Does the 12-hour daily DT rule in California apply to 16-hour shifts?

Yes. A 16-hour shift in California pays: 8 hrs straight + 4 hrs time-and-a-half + 4 hrs double-time. DT premium = 4 × base (since DT is base × 2, the "premium on top of straight time" is an additional full base × hours). On the 7th consecutive workday, the first 8 hours are OT and hours beyond 8 are DT, so a 16-hour 7th-day shift is 8 at 1.5× + 8 at 2×.

Are shift differentials always paid on "per hour worked" — or can they be flat per shift?

Both are common. Per-hour is the FLSA-compliant default and is what this calculator assumes. Flat per-shift (e.g., "$50 night shift premium regardless of hours worked") is technically problematic under FLSA because it doesn't scale correctly into the blended regular rate for OT calculations. If your employer pays flat per-shift, that shift's premium should be allocated across the hours worked in that shift when computing overtime — ask payroll how they're handling it.

Should I file a DOL complaint if I think my OT is wrong?

Start with your HR and payroll in writing (email, not verbal). If they don't correct it, file with the DOL Wage and Hour Division (federal FLSA violations) or your state Department of Labor (state-specific OT). There's no retaliation protection stronger than a documented FLSA claim — 29 U.S.C. § 215(a)(3) makes retaliation an independent cause of action.