Shift differential calculator, with the overtime math payroll gets wrong.

A shift differential is extra pay for working less popular hours, like nights, evenings, weekends or holidays. It's usually a flat amount per hour or a percentage of your base rate.

• Flat differential: $30 base + $4 night differential = $34 for each night hour.
• Percentage differential: 10% on a $30 base = $3 extra, or $33 for each qualifying hour.

Differential pay for the week = differential per hour × the hours that qualify.

This is where paychecks most often go wrong. Under the federal FLSA, shift differentials are part of your regular rate. Overtime has to be paid at 1.5 times that blended rate, not just 1.5 times your base rate.

1. Add base pay for all hours and differential pay for the qualifying hours.
2. Divide by total hours worked to get the regular rate.
3. Pay an extra half of the regular rate for every hour over 40.

Example: 48 hours at $30 with 24 night hours at +$4. Straight-time pay is $1,536 and the regular rate is $32. Overtime adds 0.5 × $32 × 8 = $128, so gross pay should be $1,664. Paying the overtime premium on the $30 base instead gives $1,656, which is $8 short every week.

Federal law doesn't require extra pay for nights or weekends. Differentials come from your employer's policy, your offer letter or a union contract. Once your employer pays one, it has to be included in your regular rate for overtime.