Convert each shift to minutes, subtract the unpaid break, add all the minutes together, and divide by 60 once at the very end. That order is the whole trick. Minutes add cleanly; clock times do not, because the right-hand column rolls over at 60 instead of at 100. And the figure payroll actually wants is decimal hours, where seven hours and forty-five minutes is 7.75 — never 7.45.
The calculation that always works
Take one day at a time and keep everything in minutes until the last step.
- Write both times in 24-hour form.
5pmbecomes17:00, and the ambiguity disappears. - Turn each into minutes since midnight: hours × 60, plus the minutes.
- Subtract the start from the end.
- Subtract the unpaid break, in minutes.
- Stop. Do not convert to hours yet.
A shift from 08:45 to 17:20 with a 30-minute lunch: the start is 525 minutes (8 × 60 + 45), the end is 1040 minutes (17 × 60 + 20), the difference is 515, and the break takes it to 485 minutes. Only now divide: 485 ÷ 60 is 8.08 hours, or 8 hours 5 minutes.
The same method across a week
The reason to hold off on dividing is that fractions of an hour are ugly to add and minutes are not. Five days, each carried through as a whole number:
| Day | Start | End | Break | Minutes |
|---|---|---|---|---|
| Monday | 08:45 | 17:20 | 30 | 485 |
| Tuesday | 09:00 | 17:30 | 45 | 465 |
| Wednesday | 08:30 | 16:00 | 30 | 420 |
| Thursday | 09:15 | 18:05 | 60 | 470 |
| Friday | 08:00 | 13:30 | 0 | 330 |
Those add to 2170 minutes. Divided by 60 that is 36.17 hours, which reads on a clock as 36 hours 10 minutes. One division, one rounding, one chance to be wrong.
Doing that by hand every Friday gets old, and it is worse if you also have to apply an overtime threshold and multiply by a rate. The weekly timesheet calculator here takes the times in whatever form you normally write them — 9, 0930, 9:30am, 17:45 — and shows the total both ways, as hours and minutes and as the decimal figure payroll will ask for. It runs in the page, so nothing about your week is uploaded anywhere. The trade is that nothing is saved either: reload and the sheet is empty.
Why 7:45 is not 7.45 hours
This is the single most expensive timesheet mistake, and it always costs the same person. Minutes are sixtieths, so you divide them by 60 rather than sliding them behind a decimal point. Writing 7:45 as 7.45 throws away 0.3 of an hour — eighteen minutes of work, per entry, gone.
The conversions worth committing to memory:
| Minutes | Decimal hours |
|---|---|
| 6 | 0.1 |
| 15 | 0.25 |
| 20 | 0.33 |
| 30 | 0.5 |
| 45 | 0.75 |
| 50 | 0.83 |
Six minutes being exactly a tenth of an hour is why payroll systems so often work in tenths rather than in ten-minute blocks. Ten minutes is 0.1667, which never comes out clean.
How do you count a shift that crosses midnight?
Add 1440 minutes — a full day — to the end time before subtracting. A shift from 22:00 to 06:15 gives a start of 1320 and an end of 375, which looks like a negative span until you treat the end as 1815. Then 1815 − 1320 is 495 minutes, or 8 hours 15 minutes.
The same arithmetic breaks down for anything longer than 24 hours, because two clock times cannot describe it: 09:00 to 09:00 could be nothing or could be a full day. Split those across two entries and label them.
Which breaks do you subtract?
Only unpaid ones. If your break is paid, subtracting it means working for free, and it is a startlingly common error on self-reported sheets — people subtract lunch out of habit whether or not the contract says to.
Under United States federal rules, short rest breaks of roughly 20 minutes or less are counted as hours worked and must be paid. A genuine meal period, usually 30 minutes or more, is unpaid only if you are actually relieved of duty for it; eating at your desk while answering the phone is not a meal period in that sense. Other countries define this differently, so check your contract before you assume.
Can your employer round your hours?
In the United States, within limits. Federal regulations permit rounding to the nearest quarter of an hour — the “seven-minute rule”, where 1 to 7 minutes round down and 8 to 14 round up — provided the practice averages out over time and does not systematically work against the employee. Rounding that only ever goes the employer's way has repeatedly lost in court.
Two practical points. Rounding is nearly always applied per punch or per entry, not to the weekly total, and those errors accumulate: round five daily entries to the nearest 15 minutes and the week can land up to 37 minutes away from the true figure in either direction. And if you are checking a payslip, round your own numbers the same way theirs are rounded before you compare, or you will be arguing about a discrepancy the policy created on purpose.
When does overtime start?
It depends where you are, and a single weekly threshold is not enough to describe it.
- United States, federal. Time and a half for hours over 40 in a workweek. There is no federal daily overtime, so a 12-hour Monday followed by a short week triggers nothing.
- California. Daily overtime on top of the weekly rule: 1.5× after 8 hours in a day, double time after 12, with separate provisions for a seventh consecutive day. A weekly-only calculation understates what is owed.
- European Union. The Working Time Directive caps the average working week at 48 hours over a reference period rather than mandating a premium. Whether extra hours pay more comes from national law or your contract.
Whatever the rule, apply it to the summed total, not to each day in isolation — unless the rule is itself a daily one, as in California.
Three things that still go wrong
Daylight saving. Twice a year the clock lies to you. On the night the clocks go forward, 22:00 to 06:00 is seven hours of real work even though the clock reads eight; when they go back it is nine. Clock arithmetic cannot see this, so on those two nights you adjust by hand.
Pay periods that are not weeks. Semi-monthly and four-weekly periods split shifts across boundaries, and a night shift that starts on the 15th and ends on the 16th belongs to whichever period your employer's policy says it does. If you need to know how many working days a period actually contains, counting the days between two dates is less obvious than it looks, mostly because of which end you include.
Reconstructing the week on Friday. Memory rounds in favour of the nice round number and against the awkward one. Write the times down as they happen, even roughly — the same reason a timer you can actually see changes how you work applies here, except the payoff is an accurate sheet rather than a finished task.
The arithmetic is not hard, it is just repetitive, which is exactly the kind of thing worth handing off. The hours calculator takes a week of start and end times, subtracts the breaks, and gives you the total as hours and minutes and as decimal hours side by side, with an optional overtime threshold and rate if you want the gross pay figure too.
If the total keeps coming out lower than the day felt, the problem may not be the addition. Does the Pomodoro Technique actually work? looks at what the evidence says about timed work blocks, and at the more useful side effect: you end the day knowing where the hours went.
Frequently asked questions
How do I add up hours and minutes worked?
Convert every shift to minutes since midnight, subtract the start from the end, take off the unpaid break, and add all the minutes together. Divide the total by 60 only at the end. Adding times in hours-and-minutes form invites carry errors because the minutes column rolls over at 60, not 100.
How do I convert 7 hours 45 minutes to decimal hours?
It is 7.75 hours. Divide the minutes by 60 rather than writing them after the decimal point: 45 ÷ 60 = 0.75. Writing it as 7.45 loses eighteen minutes of paid time on that entry alone, and the error always goes against the person who worked the hours.
How do I calculate hours worked for a night shift?
Add 24 hours to the end time before subtracting. A 22:00 to 06:15 shift becomes 1815 minus 1320 minutes, which is 495 minutes, or 8 hours 15 minutes. Shifts longer than 24 hours cannot be described by two clock times at all — split them into two entries.
Do I subtract my lunch break from hours worked?
Only if the break is unpaid. Under US federal rules, rest breaks of about 20 minutes or less count as hours worked and are paid, while a genuine meal period of 30 minutes or more is unpaid provided you are relieved of duty. Eating at your desk while still covering the phone does not qualify.
Can my employer round my hours down?
In the United States, rounding to the nearest quarter hour is permitted, but it has to be neutral: it must average out over time rather than consistently favour the employer. One-way rounding has been rejected by courts. Other countries set their own rules, so check local law and your contract.
Last updated September 19, 2026