Overtime and Shift Differential Calculator

How overtime is calculated

Under the federal Fair Labor Standards Act (FLSA), a covered employee gets at least one and a half times their regular rate of pay for every hour over 40 in a workweek. The FLSA does not require overtime for working on a weekend, a holiday or a day off as such, only for the hours over 40.

Time and a half on a plain hourly job is simple: $30 an hour becomes $45 for each overtime hour. It gets harder when part of your pay comes from differentials, because the overtime rate is worked out on the regular rate, not on the base rate.

Shift differentials and the regular rate

Federal rules count night-shift differentials and similar premiums in the regular rate, whether they are paid as a percent of the base rate or as an amount an hour (29 CFR 778.207(b)). The regular rate is the week's straight-time pay, differentials included, divided by the hours worked.

Example: 48 hours at a $40 base, with 24 night hours at +$5 and 12 weekend night hours at +$5 and +$3. Straight-time pay is $1,920 + $216 = $2,136, so the regular rate is $2,136 ÷ 48 = $44.50. The 8 overtime hours are already paid at straight time, so what is still owed is half the regular rate for each: 8 × $22.25 = $178. Total: $2,314. Worked on the base rate only, the premium would be 8 × $20 = $160, $18 less. The week mode shows both, so you can check a pay slip.

Nurses: 12-hour shifts, differentials and 8/80

On a 40-hour workweek, three 12-hour shifts are 36 hours: no federal overtime, even though each shift is long. Pick up a fourth and the week is 48 hours, 8 of them overtime, paid at one and a half times a regular rate that includes your night and weekend differentials.

Hospitals and residential care facilities may use the 8/80 system instead, if they agree it with employees before the work is done. The workweek becomes a fixed, recurring 14-day period, and time and a half is due for hours over 8 in any workday and over 80 in the period. Daily overtime already paid counts toward the over-80 hours, so the same hour is not paid twice: the calculator takes the larger of the two counts. Under 8/80, every 12-hour shift carries 4 overtime hours.

Double time

Federal law does not require double time. It comes from an employment contract, a union agreement or state law. California, for example, pays one and a half times the regular rate for hours over 8 in a workday and over 40 in a workweek, and double the regular rate for hours over 12 in a workday and over 8 on the seventh consecutive day of work in a workweek.

Other states have their own rules, and some employers pay more than the law asks. Use the Quick mode to add double-time hours at your own rate.

This is a calculator, not payroll or legal advice. Your contract, union agreement or state law may pay more.

Sources, checked September 2026:

• U.S. Department of Labor: Overtime pay
• WHD Fact Sheet #54: health care and overtime (8/80)
• WHD Fact Sheet #56A: the regular rate
• California DIR: Overtime

Related tools

• Shift Schedule GeneratorSee your own rotating, 10-hour or 12-hour shift pattern on a calendar, with hours per week, and add it to your phone as a calendar file.Open the tool
• Mileage Reimbursement CalculatorAdd up business miles for a trip, a week of visits or a month, and see the reimbursement at the 2026 IRS rate or your company's own rate.Open the tool
• Commission CalculatorWork out sales commission at a flat rate, on a tiered plan applied bracket by bracket, or split with a team, with monthly and yearly totals.Open the tool