A pay period is a payroll schedule -- weekly, biweekly, semi-monthly, or monthly. Overtime is a per-workweek calculation under the FLSA, a fixed 168-hour period the employer sets, and the two do not have to line up. Summing a biweekly pay period's hours first and applying the 40-hour threshold once to the total is a different calculation than applying the threshold separately to each of the two workweeks inside it, and the two give different answers.
An hourly employee at $20/hr works 35 hours in workweek one and 45 hours in workweek two of the same biweekly pay period -- 80 hours total, paid on one check.
| Method | Regular hours | Overtime hours | Total pay |
|---|---|---|---|
| Correct: each workweek calculated separately, then summed | 35 + 40 = 75 | 0 + 5 = 5 | $700.00 + $950.00 = $1,650.00 |
| Wrong: 80 hours summed first, threshold applied once | 40 | 40 | $2,000.00 |
The wrong method treats the whole 80-hour pay period as if it were a single workweek, so it runs the 40-hour threshold against 80 hours instead of against each week's own hours -- turning 35 straight-time hours in week one into overtime it never was, and overpaying by $350.00 on this one pay period. The direction of the error depends on the split: a week that never crosses 40 hours on its own can still get counted as overtime once it is summed into a period total that does.
Both totals use this calculator's own single-rate function, run once per workweek for the correct total and once against the summed 80 hours for the wrong one -- the only input that changes is which hours are handed to it in a single call.
Every workweek -- a fixed, recurring 168-hour period the employer designates, which does not have to align with the pay period. A biweekly pay period covers two separate workweeks, a semi-monthly period can split a single workweek across two paychecks, and the 40-hour overtime threshold applies once per workweek regardless of how the pay period is drawn around it.
The 40-hour threshold gets applied to the wrong number. A biweekly employee working 35 hours one week and 45 the next worked 80 hours total, but owes overtime for only the 5 hours past 40 in the second week -- summing first and applying one 40-hour threshold to 80 hours instead produces 40 hours of overtime, vastly overpaying, because it treats a two-week total as if it were a single workweek.
Only when neither individual workweek crosses the 40-hour threshold on its own, or when both workweeks are calculated separately and then added -- never when the two weeks' hours are added together first and the threshold is applied to that combined total. The two methods agree only in the coincidental case where summing first happens not to push the total over 40 by more than one week's overtime would have produced anyway, which is not something to rely on.
No, by design -- it calculates one workweek at a time, which is what the law actually measures. For a biweekly or semi-monthly pay period, run each workweek inside it through the calculator separately and add the results, the same way the worked example on this page does.