Pay periods explained

Biweekly and semi-monthly sound interchangeable and are not. The difference changes the size of every cheque you get — and how your overtime is worked out.

Last reviewed August 2026 · TimeWorked · General information, not legal or tax advice

The four schedules

SchedulePaydays a yearPeriod coveredPayday falls on
Weekly527 daysThe same weekday every week
Biweekly2614 daysThe same weekday, every other week
Semi-monthly24Half a monthFixed dates, e.g. the 15th and the last day
Monthly121 calendar monthA fixed date each month

Biweekly versus semi-monthly

These two get confused constantly, and the difference matters more than it looks.

Because 26 > 24, a biweekly cheque is smaller than a semi-monthly one at the same salary. On $52,000 a year, biweekly pays $2,000.00 and semi-monthly pays $2,166.67. The annual total is identical.

Biweekly also produces the famous "three-paycheck months": two months in most years contain three biweekly paydays. It feels like a bonus, but it is simply the 26-payday cycle catching up with the 12-month calendar.

For hourly employees, biweekly is usually the better fit. A biweekly period always contains exactly two complete workweeks, so overtime lines up cleanly. A semi-monthly period slices through the middle of workweeks, and because overtime must still be computed per workweek — not per pay period — payroll has to split hours across cheques. That is a common source of miscalculated overtime.

The workweek is not the pay period

A workweek is a fixed, recurring period of 168 consecutive hours. Your employer chooses when it starts, and it does not have to be Monday or align with the pay period at all. Overtime is calculated inside each workweek, on its own.

This is why the answer to "did I work overtime?" never depends on your pay schedule. If your workweek runs Sunday to Saturday and you worked 45 hours in it, you are owed 5 hours of premium — whether that week sits neatly inside one cheque or is split across two.

Find out which workweek your employer uses before you try to reconcile a pay stub. It is often in the handbook; if not, ask. Setting the same start day in the timesheet calculator makes your totals line up with theirs.

The 27-paycheck year

Because 26 biweekly periods cover 364 days and a year is 365 or 366, biweekly paydays creep forward by a day or two annually. Roughly every 11 years the drift accumulates enough that a calendar year contains 27 biweekly paydays instead of 26. Weekly payrolls hit the same problem with a 53rd payday.

For hourly employees this is a non-event — you are paid for hours worked, so an extra payday just means an extra period of hours. For salaried employees it is a real decision for the employer: divide the annual salary by 27 (each cheque shrinks), keep the normal amount (the year costs about 3.8% more), or adjust the following year. Whichever they choose, it should be communicated in advance.

Pay dates and lag time

Nobody is paid the instant a period closes. The gap between the end of a pay period and the payday is the lag or arrears period, typically 3 to 10 days, and it exists so payroll can collect, approve and process timesheets.

Two consequences worth knowing:

State law also sets minimum pay frequencies. Many states require at least semi-monthly payment, some require weekly for manual workers, and monthly-only payroll is restricted or prohibited in several places.

Choosing a schedule

ScheduleBest forWatch out for
WeeklyHourly and variable-hour staff; industries with high turnover52 payroll runs a year — the highest processing cost
BiweeklyMost hourly workforces; clean overtime alignmentThree-payday months and the occasional 27th period
Semi-monthlySalaried staff; matches monthly accountingOvertime split across cheques; paydays land on weekends
MonthlyExecutives, some international payrollsRestricted or prohibited for many employees by state law

Use the hourly to salary calculator to see the same annual figure divided across all four schedules.

Frequently asked questions

What is the difference between biweekly and semi-monthly pay?

Biweekly is every 14 days, giving 26 paydays a year on a fixed weekday. Semi-monthly is twice a calendar month on fixed dates, giving 24 paydays. Semi-monthly cheques are larger; the annual total is the same.

How many pay periods are there in a year?

52 weekly, 26 biweekly, 24 semi-monthly or 12 monthly. Roughly once a decade a calendar year contains a 27th biweekly or 53rd weekly payday because of calendar drift.

Why did I get three paychecks this month?

You are paid biweekly. Twenty-six paydays do not divide evenly into twelve months, so two months in most years contain three of them. It is not extra money — the annual total is unchanged.

Is overtime calculated per pay period or per week?

Per workweek, always. A workweek is a fixed 168-hour period chosen by your employer. Even on a semi-monthly schedule that splits a week across two cheques, the overtime must still be worked out on the full workweek.

What is a 27 pay period year?

A calendar year that happens to contain 27 biweekly paydays instead of 26, because 26 periods cover only 364 days. Employers either divide the annual salary by 27, absorb the extra cost, or adjust the following year.

Why is my first paycheck at a new job smaller?

You started part-way through a pay period, and payroll runs in arrears — there is normally a lag of several days between a period closing and the payday, so the first cheque covers only the days you actually worked.

Sources

Keep reading

Hourly ↔ salary

Convert an hourly rate to annual pay and back.

Overtime laws by state

Federal rules plus the states that add daily or lower thresholds.

PTO accrual

Turn an accrual rate into days and a year-end balance.

Work hours in a year

Where 2,080 comes from, and the months that break it.

Weekly timesheet

A full week with breaks, overtime, saving and export.