The federal baseline is the Fair Labor Standards Act, and it is a weekly rule. Covered non exempt employees are owed at least one and a half times their regular rate for every hour worked beyond 40 in a workweek. The workweek is a fixed, recurring period of seven consecutive 24 hour days that your employer sets, and it does not have to line up with the calendar week or with your pay period.
The formula
Overtime pay = hourly rate x 1.5 x overtime hours
Worked example
Someone on $22 an hour works 46 hours in one week. The first 40 hours pay $880. The six extra hours pay $33 each, which is $198. The week comes to $1,078 gross, and the effective average rate across all 46 hours is about $23.43.
Two details catch people out. The first is that overtime is based on your regular rate, not your base rate, and the regular rate includes things like nondiscretionary bonuses and shift differentials averaged across the hours you worked. If you earned a production bonus in a week with overtime, your overtime is worth slightly more than the quick calculation above. The second is that paid time off does not count toward the 40 hour threshold, because those hours were not worked. A week with eight hours of vacation and 36 hours at work is a 44 hour paycheck with no overtime in it.
$15 an hour
$22.50
overtime rate
$18 an hour
$27.00
overtime rate
$20 an hour
$30.00
overtime rate
$25 an hour
$37.50
overtime rate
$30 an hour
$45.00
overtime rate