The United States has guidelines that regulate how much an employee must be paid and how much, regardless of industry -- these are American minimum wage and general labor laws. Workers who are part time sometimes are confused about when they are entitled to overtime pay, as the law doesn't specifically address part-time workers and overtime.
FLSA and Full Time
The Fair Labor Standards Act is the primary legislation that discusses overtime pay in the United States. The FLSA technically does not define full time but rather states that you are entitled to overtime pay after 40 hours. Because employers must pay employees time and a half for overtime, most employers adopt 40-hour work weeks in order to manage costs.
FLSA and Part Time
The FLSA is completely silent on overtime hours for part-time workers. Employers typically fall back on the 40-hour standard. This means that it doesn't matter if you are considered part time or full time -- you are entitled to overtime after working 40 hours in a week, as asserted by the North Carolina Department of Labor.
If you are a part-time employee, it is tempting to view hours worked in addition to your usual hours as overtime, but this really isn't the case, according to the FLSA. If you work more than you usually do but fewer than 40 hours, you usually are entitled to compensation at your usual hourly rate. Once you go past 40 hours in a week, employers are obligated under the FLSA to pay you time and a half.
Part-time employees usually work 10 (quarter-time), 20 (half-time), or 30 hours (three-quarter time) a week. If you work quarter-time, you need 30 more hours to reach overtime. At half time, you'd need 20. If you work three-quarter time, you must work an extra 10 hours before your employer has to pay you extra. Of course, many employees fall somewhere between these general part-time classifications, so the best way to determine when overtime applies is to subtract the number of hours you've worked from 40. The only real exception to this is if your contract specifically states you are to receive higher pay at a point less than 40 hours per week -- this is at the discretion of your employer, and most simply follow the FLSA.