Minutes to Hours

The most frequent error is reading 1.5 hours as 1 hour 50 minutes. The decimal part is a fraction of 60, not of 100: 0.5 h is 30 minutes, 0.25 h is 15 minutes, 0.1 h is 6 minutes and 0.75 h is 45 minutes. So 1.5 hours is 1:30, and 1:50 is 1.833 hours.

To go from a decimal back to clock time, multiply only the fractional part by 60: 3.4 h becomes 3 hours plus 0.4 × 60 = 24 minutes, or 3:24. The hours to minutes page works through that direction in detail.

Payroll systems multiply a decimal number of hours by an hourly rate, so minute totals must be converted first. A week of 38 h 45 min is 38.75 hours; at $24 an hour that is $930, whereas typing 38.45 would underpay by $7.20. Many time clocks round each punch: US federal wage rules allow rounding to the nearest 5 minutes, tenth of an hour or quarter hour, provided it evens out over time rather than always favoring the employer.

With quarter-hour rounding, 1 to 7 minutes round down and 8 to 14 minutes round up, the so-called 7-minute rule. Lawyers and consultants usually bill in tenths of an hour, so a 14-minute call is billed as 0.3 h, since the minimum unit is 6 minutes and work is rounded up to the next unit. Time a task with the stopwatch if you need the raw minutes.