How this instrument works
Semi-monthly payroll pays on two fixed calendar dates a month — commonly the 15th and the last business day — for 24 checks a year, and this instrument performs exactly that division: the annual salary entered, split into 24 equal parts. It is the schedule most salaried, exempt employees and much of government payroll actually run, chosen because it lines up cleanly with monthly accounting cycles and fixed benefit deductions rather than with a rolling calendar of weeks.
Because the dates are fixed rather than the day count, the two halves of a month are rarely the same length: a 31-day month splits into a 15-day stretch and a 16-day stretch, a 30-day month splits evenly, and February splits into two even shorter halves. Each half still pays exactly the same amount — the formula divides by 24, not by days elapsed — so a paycheck covering 16 days is worth precisely as much as one covering 14. That is a genuinely different kind of unevenness from a biweekly calendar, where every period runs a fixed 14 days but the number of paychecks in a given month can rise to three.
The figure returned is gross pay: before federal and state withholding, Social Security and Medicare, or any benefit premium reduces what is actually deposited. It also assumes a clean 24-period year with no partial first or final paycheck for someone hired or terminated mid-period — proration for those cases is a separate calculation this sheet does not attempt.
- Enter your yearly gross salary into Annual salary, $ — the figure from an offer letter or a W-2, not a per-check amount.
- Read Semi-monthly pay (24/year), $ for the exact amount one of the 24 paychecks carries, before any withholding.
- Count the paychecks on a recent pay stub for one year — if it lands on 24, this figure should match; if it lands on 26, the schedule is biweekly instead.
- Adjust Annual salary, $ to see how a raise, a counteroffer, or a new role changes both fixed monthly paychecks at once.
Worked example — a $60,000 salary
Enter 60000 into Annual salary, $. Split across the 24 periods a semi-monthly calendar runs, Semi-monthly pay (24/year), $ reads exactly $2,500.00 — one check landing around the 15th of the month and a second on the last business day, every month, all year, with no exceptions for longer or shorter halves.
Run the same $60,000 through a biweekly schedule instead and it divides by 26, not 24, giving $2,307.69 a check — smaller, because 26 periods slice the year thinner than 24 does. A payroll administrator setting up a new hire's calendar, or a candidate comparing two offers quoted only as a per-check figure, can misread that gap as a pay difference when it is really just a difference in how many checks the same annual number gets cut into.
Questions
How is semi-monthly pay different from biweekly pay?
Semi-monthly means twice a month on fixed calendar dates — typically the 15th and the last day — for 24 paychecks a year; biweekly means every two weeks for 26. The same $60,000 salary yields $2,500.00 semi-monthly but $2,307.69 biweekly: fewer, larger checks under the semi-monthly calendar because the year is cut into 24 pieces instead of 26. Offer letters rarely spell out which is meant, and treating the two as interchangeable is a common paycheck-budgeting error.
Why do semi-monthly paychecks sometimes cover 15 days and sometimes 16?
Because a semi-monthly period is bounded by dates, not by a fixed day count. A 31-day month splits into a 15-day first half and a 16-day second half; a 30-day month splits 15 and 15; February splits into two shorter halves still. Every half pays the identical amount regardless — the formula divides the annual salary by 24, not by days elapsed in the period.
Does semi-monthly pay ever produce a three-paycheck month?
No. Twenty-four periods split evenly into twelve months, two apiece, every month, all year — unlike a biweekly schedule, whose 26 periods occasionally stack a third paycheck into two months a year. That fixed two-per-month rhythm is one reason accounting departments favor semi-monthly payroll for budgeting, even though the number of calendar days behind each check still shifts.
Is Semi-monthly pay (24/year), $ shown before or after tax?
Before. It is gross pay — before federal and state withholding, Social Security and Medicare, and any benefit premium reduce what actually lands in an account. Net pay on a real check will be smaller, by an amount that depends on filing status, state, and the withholding elections made with an employer.
Why would an employer run semi-monthly payroll instead of biweekly?
Mostly for administrative consistency: semi-monthly payroll always closes on the same two calendar dates, which lines up cleanly with monthly accounting, benefit deductions, and salaried contracts. Biweekly payroll is more common for hourly staff because its fixed 14-day windows track overtime more cleanly than a semi-monthly calendar's uneven period lengths do.
My salary isn't a round number — will my 24 paychecks still match exactly?
Yes. This instrument divides the annual figure by 24 and rounds only the final result to the cent, so every paycheck comes out the same amount. A $61,000 salary pays $2,541.67 each period; any leftover fraction of a cent from a full year of that rounding is typically absorbed once, in a single paycheck, by real payroll software rather than spread unevenly across all 24.
References
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.