Hours Calculator

Fill in when you started and finished, put the break in, and the week adds itself up. Nothing is sent anywhere, so a rota with real names and real hours on it stays on your machine.

Decimal hours are not clock hours

7 hours 30 minutes

on a clock     7:30
in decimal     7.50
written wrong  7.30   (7 hours 18 minutes)

The last one is the mistake that costs money. It
looks right, adds up in a spreadsheet, and is
twelve minutes short every time it appears.

This is the single most common error in a hand-kept timesheet. Half an hour is 0.5 of an hour and 30 minutes on a clock, and writing 7.30 for seven and a half hours turns it into seven hours and eighteen minutes. The arithmetic then works perfectly and gives the wrong answer.

Payroll systems almost always want decimal, and people almost always think in clock time, so both are shown here side by side. Everything is worked out in whole minutes underneath and only converted at the very end, which keeps the rounding in one place instead of accumulating.

The conversion, if you need it by hand

:00  .00      :20  .33      :40  .67
:05  .08      :25  .42      :45  .75
:10  .17      :30  .50      :50  .83
:15  .25      :35  .58      :55  .92

Only the quarters land on a tidy decimal. The
rest recur, so payroll systems round them.

Divide the minutes by 60. Twenty minutes is a third of an hour, which is 0.3333 recurring, so it has to be rounded somewhere. Two decimal places is what most payroll software uses and is what is shown here.

The tenth-of-an-hour rounding in the settings exists for the same reason. Six minutes is exactly 0.1 hours, so a system that rounds to six minute blocks never produces a recurring decimal, which is why so many of them do it.

Night shifts

Clock on   22:00
Clock off  06:00

06:00 minus 22:00 = minus sixteen hours

Which is why a spreadsheet gives you ####. The
shift crossed midnight, so it is eight hours,
and this counts it that way without being asked.

A finish time earlier than the start time means the shift ran past midnight. That is a night shift, not a typo, and it gets counted across the boundary and labelled so you can see it happened. Nobody working nights should have to add 24 by hand every week.

A shift that ends exactly at midnight can be written either way. Put 00:00 and it reads as the end of the day, and 24:00 works too if that is what your rota says.

Rounding, and who it favours

Worked 7 hours 52 minutes, rounded to 15 minutes

nearest   7:45     you lose 7 minutes
up        8:00     you gain 8 minutes
down      7:45     you lose 7 minutes

Over 250 shifts, rounding down to the quarter
costs about 29 hours. It is worth knowing which
way your employer does it.

Plenty of employers round clock-in times, and it is legal in most places as long as it is neutral over time. Rounding to the nearest quarter of an hour evens out. Always rounding down does not, and in the United States that practice has lost several large wage cases.

The rounding here is applied to each shift before the break comes off, which is how a clock-in system does it. If your employer rounds a different way the totals will differ slightly, and the exact minute setting shows you what was actually worked.

Overtime

Overtime is counted on the weekly total, over whatever threshold you set, which is the ordinary arrangement and the one used in the United States under the Fair Labor Standards Act. Forty hours and time and a half are the defaults.

Some places count overtime daily instead, over eight hours in a single day, and a few count both and pay whichever is higher. This does not do daily overtime, so if that is your situation the weekly figure will be low. Better you hear that here than work it out from a wrong number later.

What this is not

It is a calculator, not a payslip. It knows nothing about tax, national insurance, pension contributions, holiday accrual or unsocial hours premiums, and the pay figure is gross pay before any of that. Treat it as a way to check your own arithmetic instead of as a source of truth.