In the US, non-exempt employees earn 1.5× their regular rate for hours over 40 per week (FLSA).
Overtime rate = regular hourly rate × 1.5. Overtime pay = overtime rate × overtime hours.
Federal law requires time-and-a-half (1.5×), not double. Some states or employers pay more.
Generally non-exempt employees working over 40 hours/week. Exempt salaried workers typically do not.