Calculating hours worked from clock times, by hand

Turning a clock-in and clock-out time into hours worked looks like simple subtraction, and for a normal daytime shift, it is. Two things complicate it in practice: an unpaid break has to come off the total, and a shift that runs past midnight makes the "end minus start" subtraction go negative unless you account for the day rolling over.

The method

1. Convert both clock times to minutes since midnight (hours × 60 + minutes).
2. Subtract start from end to get the span. If the result is negative, the shift crossed midnight — add 1,440 minutes (24 hours) to correct it.
3. Subtract the unpaid break, in minutes, from that span.
4. Convert the worked minutes back to hours and minutes (divide by 60 for hours, take the remainder for minutes), or to a decimal (divide by 60) for payroll.

In one line: worked minutes = (end − start, +1440 if negative) − break minutes.

A worked example: a daytime shift

Clock in 09:00, clock out 17:30, with a 30-minute break.

In minutes: start 9 × 60 = 540, end 17 × 60 + 30 = 1,050. Span: 1,050 − 540 = 510 minutes. Minus the break: 510 − 30 = 480 minutes worked, which is 480 ÷ 60 = 8 hours exactly — 8h 0m, or 8.00 as a decimal.

A worked example: an overnight shift

Clock in 22:00, clock out 06:00 the next morning, with a 45-minute break.

In minutes: start 22 × 60 = 1,320, end 6 × 60 = 360. Span: 360 − 1,320 = −960 — negative, so add 1,440: −960 + 1,440 = 480 minutes. Minus the break: 480 − 45 = 435 minutes, which is 435 ÷ 60 = 7.25 hours — 7h 15m.

The mistake worth watching for

Treating a negative span as "the shift must be wrong" instead of "the shift crossed midnight" is the most common slip, and it goes the other way too: a break longer than the shift itself is an input mistake, not a night shift, and should stop the calculation rather than silently wrapping into a nonsense number of hours.

The free Time Duration tool runs this same subtraction — including the overnight wrap and the break-longer-than-shift check — for any start time, end time and break length.