Hours between two times
Start and finish. The answer comes out both ways — as hours and minutes, and as the decimal hours a timesheet wants — because those are different numbers and mixing them up is the most expensive mistake on any payroll.
This one runs on your own device. It is worked out in your browser, so there is nothing to send and nothing to log. Where a tool on this site does send something out, that page says so and names where it goes.
7.30 is not seven and a half hours
Seven hours and thirty minutes is 7.5
decimal hours, because thirty minutes is half of sixty. Writing it as
7.30 on a timesheet claims seven hours and eighteen minutes
— the clock runs in sixties and the decimal point does not.
Twelve minutes a day, five days a week, is an hour a week. This is the single most common way people are underpaid by arithmetic rather than by anybody's intention, so both figures are given here and neither is left for you to convert.
Shifts that cross midnight
Ten at night to six in the morning is eight hours, but subtracting one clock time from the other gives minus sixteen. A calculator that hands you a negative number has understood the arithmetic and not the question.
Where the finish is earlier on the clock than the start, this assumes you finished the next day, which is the only reading that makes sense of a night shift. It says so on the reading, so that if you meant something else you can see that it guessed.
Rounding, and who it favours
Many employers round timesheets to the nearest quarter of an hour. Rounding to the nearest is even-handed: over enough days the ups and downs cancel. Rounding down every time is not, and eight minutes a day is nearly an hour a fortnight.
The option above rounds to the nearest, and the reading always shows the unrounded figure beside it so you can see what the rounding did.
What this does not do
One span at a time, and no pay. It does not add up a week of shifts, work out overtime, or apply a rate — for turning hours into money there is the salary converter.
Nor does it know the law. Britain gives most workers a twenty-minute break after six hours and limits the average working week, but the detail depends on your age, your job and your contract, and a calculator is the wrong place to learn it.