The minute field in military time counts sixtieths of an hour, not tenths. 1750 is 17 hours and 50 minutes, not 17.5 hours. This chart converts minutes to decimal hours correctly, every time.

The Base-60 Trap That Breaks Payroll

Military time uses a base-60 minute field. Minutes run 00 to 59 and count sixtieths of an hour. Decimal hours run on base-10 and count tenths.

Neither system is wrong. They cannot be substituted for one another.

The hour field never changes value in conversion. It runs 00 to 23 and maps directly to decimal hours. The minute field is where payroll errors breed. Because minutes are base-60, the four digits of military time as a whole are not a normal number. 1759 is followed by 1800, not 1760. No arithmetic that assumes otherwise survives contact with a real timesheet.

Payroll converts minutes to decimals for one reason: an hourly rate multiplies cleanly in base-10, but not in base-60. Thirty minutes becomes 0.5 hours. Forty-five becomes 0.75. The conversion applies only to a duration, never to a clock reading.

Minutes to Decimal Conversion Chart: 00 to 59

Minutes Decimal Hours Minutes Decimal Hours Minutes Decimal Hours
00 0.000 20 0.333 40 0.667
01 0.017 21 0.350 41 0.683
02 0.033 22 0.367 42 0.700
03 0.050 23 0.383 43 0.717
04 0.067 24 0.400 44 0.733
05 0.083 25 0.417 45 0.750
06 0.100 26 0.433 46 0.767
07 0.117 27 0.450 47 0.783
08 0.133 28 0.467 48 0.800
09 0.150 29 0.483 49 0.817
10 0.167 30 0.500 50 0.833
11 0.183 31 0.517 51 0.850
12 0.200 32 0.533 52 0.867
13 0.217 33 0.550 53 0.883
14 0.233 34 0.567 54 0.900
15 0.250 35 0.583 55 0.917
16 0.267 36 0.600 56 0.933
17 0.283 37 0.617 57 0.950
18 0.300 38 0.633 58 0.967
19 0.317 39 0.650 59 0.983

How to Use This Chart

A shift recorded from 0900 to 1730 is first reduced to a length of eight hours thirty minutes. Only then does it become 8.5 hours for the payroll run. Reversing those steps, converting the clock times themselves, produces figures that are meaningless.

The process is always:

  1. Convert the clock readings to a duration.
  2. Keep the whole hours.
  3. Find the remaining minutes in the chart.
  4. Add the decimal to the whole hours.

A shift from 0815 to 1645 is eight hours thirty minutes. That is 8.5 hours. Not 8.45. Not 8.75. The 45 minutes of the end time has nothing to do with the duration's minute count.

1750 Is Not 17.50

1750 is a point in the day. Fifty minutes past five in the evening.

17.50 hours is a length of time. Seventeen and a half hours.

The first is a clock reading. The second is a quantity. The gap between them is twenty minutes. On a payroll of any size, twenty minutes repeated across a fortnight is real money.

Converted honestly, the clock reading 1750 corresponds to 17.833 decimal hours. Fifty minutes is five-sixths of an hour. The error is easy to make because it requires no mistake in reading military time at all, only in assuming the four digits behave like a decimal number. They do not.

17.5 hours is 1730 in military time. Thirty minutes is exactly half an hour. The same class of error treats 1.45 hours and one hour forty-five minutes as equal. The true decimal value of the latter is 1.75.

Quick Mental Math Shortcuts

These five-minute intervals cover almost every real timesheet:

Minutes Decimal Exact?
05 0.083 Recurring
10 0.167 Recurring
15 0.25 Exact
20 0.333 Recurring
25 0.417 Recurring
30 0.5 Exact
35 0.583 Recurring
40 0.667 Recurring
45 0.75 Exact
50 0.833 Recurring
55 0.917 Recurring

Fifteen, thirty, and forty-five are the only exact values in the five-minute set. Everything else recurs and has to be rounded. That is why payroll rules specify how many decimal places are carried and in which direction.