Hours worked are the time from the start of a shift to its end, less any unpaid break. The calculator counts in whole minutes, the resolution of a clock, and shows the answer three ways: hours and minutes, the h:mm form a timesheet uses, and decimal hours, which is what payroll multiplies by an hourly rate.
Decimal hours. Minutes become a decimal by dividing by 60, so 15 minutes is 0.25 of an hour, 30 minutes 0.5 and 45 minutes 0.75. The one that catches people out is 20 minutes: it is 0.33 hours, not 0.20. So 7 h 20 min is 7.33 hours, and at $20 an hour that shift pays $146.67, not $144.
Night shifts. When the end time is earlier than the start, the shift has run past midnight, and the calculator adds a day: 22:00 to 06:00 is 8 hours. A start and end at the same time counts as no time rather than 24 hours; for a full-day shift, split it into two entries. The one thing it cannot see is a daylight-saving change, which adds or removes an hour on the night the clocks move.
Timesheets. The weekly table totals each day the same way and adds them up, so five days of 9:00 to 17:30 with a half-hour lunch comes to 40 hours. Days left empty count as zero. Check your employer's rounding rule before you submit: some round each punch to the nearest 5, 6 or 15 minutes, which can move the total either way.