29 CFR §810.125

1. (a)General. If any worker performing direct production work is compensated by a method other than hourly, such as a salary, piece-rate, or day-rate basis, the worker's hourly base wage rate shall be calculated by converting the salary, piece-rate, or day-rate to an hourly equivalent. This hourly equivalent is then multiplied by the number of hours worked in direct production for purposes of calculating the average hourly base wage rate.
2. (b)Examples.
   1. (1)Where the salary, piece-rate, or day-rate wage is paid to a worker on a weekly or bi-weekly pay period basis, the total salary, piece-rate, or day-rate compensation for that pay period will be divided by the total number of hours worked in the pay period to determine the hourly equivalent.
   2. (2)Where the salary, piece-rate, or day-rate wage is paid to a worker on a semi-monthly pay period basis, the total salary, piece-rate, or day-rate compensation will be converted to a weekly equivalent by multiplying the compensation by 24 (semi-monthly pay periods in a year) and dividing by 52 (weeks per year). This weekly equivalent will be divided by the total number of hours worked in the week to determine the hourly equivalent.
   3. (3)Where the salary, piece-rate, or day-rate wage is paid to a worker on a monthly pay period basis, the total salary, piece-rate, or day-rate compensation will be converted to a weekly equivalent by multiplying the compensation by 12 (monthly pay periods in a year) and dividing by 52 (weeks per year). This weekly equivalent will be divided by the total number of hours worked in the week to determine the hourly equivalent.