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By Jamie Reeves, Personal Finance Writer

Why Are Paychecks Biweekly?

A calendar showing two workweeks fitting exactly inside one pay period

Because two weeks is the shortest pay period that is both a whole number of workweeks and cheap enough to run. No federal law requires any particular frequency — but federal law does fix the workweek, and overtime is computed inside it. A biweekly period is exactly two of them. Semi-monthly is not a whole number of anything.

Federal law sets no pay frequency at all

This surprises people who assume biweekly is a legal default. The Fair Labor Standards Act sets a minimum wage and overtime rules; it does not say how often you must be paid. The federal requirement is regularity — wages are due on the regular payday for the period the work fell in.

Frequency is a matter of state law, and it varies. Some states require at least semi-monthly payment, some set different floors for different classes of worker, and some say very little. Your state labor department publishes the rule that actually governs you; it is the only one that does.

What federal law does fix: the workweek

Here is the piece that explains the pattern. Overtime is not computed over a month, or a pay period, or an average. It is computed over a workweek, and the regulation defines that precisely.

“An employee’s workweek is a fixed and regularly recurring period of 168 hours — seven consecutive 24-hour periods.”
— 29 CFR 778.105

And each one is judged on its own, under 29 CFR 778.104: a workweek stands alone, so hours cannot be averaged across two of them to avoid overtime. Fifty hours one week and thirty the next is ten hours of overtime, not a tidy eighty.

That is the constraint the pay period has to live with. If your pay period contains a whole number of workweeks, every overtime calculation falls neatly inside one payslip. If it does not, workweeks straddle the boundary and have to be tracked across two.

Why semi-monthly is awkward, and for whom

FrequencyPeriods / yearWhole workweeks?Payday lands on
Weekly52Yes — onesame weekday
Biweekly26 (sometimes 27)Yes — twosame weekday
Semi-monthly24No — ~15.2 daysmoves around the week
Monthly12Nofixed date

A semi-monthly period averages about 15.2 days, so its boundaries fall mid-week by design. Every month, at least one workweek is cut in half by a payday. For salaried staff that costs nothing, because no overtime arithmetic is involved. For an hourly payroll it is a recurring reconciliation. That is the whole reason semi-monthly is common in salaried offices and rare on shop floors — not tradition, arithmetic.

So why not weekly?

Weekly satisfies the workweek rule perfectly and is better for the employee, because money arrives sooner and more often. It is simply twice as expensive to run: each payroll cycle carries fixed processing, filing and reconciliation costs, and 52 of them cost roughly double 26.

Biweekly is a compromise, and it is the payer’s compromise. It is the cheapest schedule that keeps overtime clean. Worth saying plainly, because it is usually presented as a neutral convention rather than a cost decision.

The leftover day, and the 27th paycheck

Twenty-six biweekly periods cover 364 days. A year is 365, or 366 in a leap year. That spare day accumulates, and roughly every eleven years a 27th payday lands inside the calendar year. Nothing has gone wrong and no one has gained a bonus — a salary is being divided into 27 payments instead of 26, so each is slightly smaller unless the employer handles it another way. We worked the arithmetic through in the 27-paycheck year.

What to check on your own payslip

Two things. First, whether your employer has designated a workweek at all — it must be fixed and recurring, and it does not have to start on Monday or at midnight. Second, whether your pay period boundary matches it. If you are hourly and your period is semi-monthly, overtime for a split workweek is the calculation most likely to be wrong, and it is the one worth checking against your own hours.

General information, not legal advice, and not specific to any state. Regulatory citations were read from the eCFR on 6 September 2026. Pay-frequency requirements are set by state law and change; your state labor department publishes the rule that applies to you.

Related

Frequently Asked Questions

Because two weeks is the shortest period that is both a whole number of workweeks and cheap enough to run. Federal law sets no pay frequency at all — it requires only that paydays be regular. What federal law does fix is the workweek: 29 CFR 778.105 defines it as a fixed and regularly recurring period of 168 hours, seven consecutive 24-hour periods, and 29 CFR 778.104 requires each workweek to stand alone when overtime is computed. A biweekly period is exactly two of those, so overtime falls cleanly inside it. Weekly would also work but costs twice as much to process. Biweekly is where the arithmetic and the cost meet.
No. The Fair Labor Standards Act sets a minimum wage and overtime rules but does not prescribe how often you must be paid. The federal requirement is regularity — wages are due on the regular payday for the pay period covered. Pay frequency is set by state law instead, and it varies: some states require at least semi-monthly payment, some set different minimums for different classes of worker, and some are largely silent. Your state labor department publishes the rule that actually governs you, and it is the only one that does.
Because a semi-monthly period is not a whole number of workweeks. Twenty-four periods a year means each one averages about 15.2 days, so pay periods start and end mid-week and the boundary lands in the middle of a workweek. Since overtime must be computed per workweek and each workweek stands alone, a workweek split across two pay periods has to be tracked across both and reconciled. That is why semi-monthly is common for salaried staff, where the arithmetic does not arise, and much less common for hourly payrolls, where it arises every month.
Because 26 biweekly periods cover 364 days and a year is 365, or 366 in a leap year. That spare day accumulates, and roughly every eleven years it pushes a 27th payday into the calendar year. Nothing has gone wrong and your annual salary has not changed — if you are salaried, the same yearly amount is being divided into 27 payments instead of 26, so each one is slightly smaller unless your employer chooses to handle it differently. It is a calendar artifact of dividing 365 by 14, nothing more.
For cash flow, no — weekly is better, because money arrives sooner and more often. Biweekly is better for the employer, because each payroll run carries fixed processing costs and running 26 of them costs less than 52. The compromise favours the payer, which is worth naming plainly. What biweekly does give the employee is predictability: the same weekday every two weeks, which makes rent and direct debits easy to line up. Semi-monthly, by contrast, moves around the week.
Usually yes, provided the new frequency still satisfies state law and the change applies going forward rather than backwards. What an employer cannot do is delay wages already earned past the regular payday for the period that covered them. Some states require advance notice of a change to payday, and a contract or collective agreement can remove the employer's discretion entirely. If a frequency change arrives with a gap where a payday should have been, that gap is the part worth questioning.
Semi-monthly suits monthly bills better, because two payments a month line up with a monthly rent or mortgage. Biweekly suits weekly rhythms better and produces two months a year with three paychecks, which people often treat as a bonus even though it is the same annual money arriving on a different schedule. Neither pays more. The practical difference is only which of your obligations the timing happens to match, and that depends on your bills rather than on the payroll system.