How to convert time to decimal hours
Decimal time expresses minutes as a fraction of an hour instead of as a count out of 60. The conversion is one step: divide the minutes by 60 and add the result to the whole hours.
The reason this trips people up is that clocks are base 60 while decimals are base 10. Everything else in daily life counts in tens, so the instinct is to read "7:45" and write "7.45" — but 0.45 of an hour is 27 minutes, not 45. That single slip is the most expensive mistake in timesheet handling, and it's covered in detail below.
Why payroll wants decimals at all
Because pay is a multiplication. Gross pay is hours × rate, and you cannot multiply "7 hours 45 minutes" by an hourly rate directly — base 60 doesn't survive the arithmetic. Converting to 7.75 first makes it trivial: 7.75 × $22 = $170.50.
The same applies to any billing by time. Law firms, agencies, consultants, and contractors all invoice in decimal hours for exactly this reason, which is why timesheet software almost universally stores decimals internally even when it displays hours and minutes.
Minutes to decimal reference table
The values below repeat every hour, so this table covers every conversion you'll need. The bolded rows are the quarter-hour marks worth committing to memory.
| Min | Dec | Min | Dec | Min | Dec |
|---|---|---|---|---|---|
| 1 | 0.02 | 21 | 0.35 | 41 | 0.68 |
| 5 | 0.08 | 25 | 0.42 | 45 | 0.75 |
| 6 | 0.10 | 30 | 0.50 | 48 | 0.80 |
| 10 | 0.17 | 35 | 0.58 | 50 | 0.83 |
| 12 | 0.20 | 36 | 0.60 | 55 | 0.92 |
| 15 | 0.25 | 40 | 0.67 | 59 | 0.98 |
| 20 | 0.33 | 42 | 0.70 | 60 | 1.00 |
Three of these are worth knowing without looking: 15 minutes is 0.25, 30 is 0.50, and 45 is 0.75. Between them they cover most rounded timesheet entries. The 6-minute mark being exactly 0.10 is also useful — it's why tenth-of-an-hour billing exists in professional services.
Worked example — a week of shifts
Monday 8 h 15 m, Tuesday 7 h 50 m, Wednesday 8 h 00 m, Thursday 6 h 40 m, Friday 8 h 25 m.
Converted: 8.25 + 7.83 + 8.00 + 6.67 + 8.42 = 39.17 decimal hours.
At $22 an hour that's $861.67 gross.
Worth noting: multiplying the displayed 39.17 by 22 gives $861.74 — seven cents more than the exact total. Tiny here, but it's the same rounding drift multiplied across every employee on a payroll run, which is why systems total the raw minutes and convert once at the end.
Payroll rounding and the 7-minute rule
Many employers don't pay to the exact minute. Instead they round each entry to a fixed increment — most commonly the quarter hour. Under US federal law this is permitted, with an important condition attached.
The mechanics, known as the 7-minute rule, work like this: time is rounded to the nearest 15-minute mark, with the first 7 minutes rounding down and 8 minutes or more rounding up.
| Minutes past the quarter | Rounds to | Effect |
|---|---|---|
| 1–7 minutes | Down | Employee loses up to 7 min |
| 8–14 minutes | Up | Employee gains up to 7 min |
The legal condition is that rounding must be neutral over time. Under the Fair Labor Standards Act, rounding is acceptable only if it doesn't systematically favour the employer — it must cut both ways across the workforce and across pay periods. A system that always rounds down, or that rounds clock-ins up but clock-outs down, is not compliant. Several states apply stricter standards than the federal rule, and California in particular has moved sharply against rounding practices in recent years.
If you're setting payroll policy: the safest position now is to pay actual recorded time. Timekeeping systems capture exact minutes automatically, so the original justification for rounding — that adding up handwritten cards was laborious — has largely disappeared. Rounding survives mostly as inherited practice, and it carries legal exposure that exact time simply doesn't.
The 7.45 mistake, and what it costs
Here is the error worth understanding properly, because it's silent and it repeats.
Someone works 7 hours 45 minutes and types 7.45 into the timesheet. The correct figure is 7.75. The gap is 0.30 of an hour — 18 minutes of unpaid work.
What that compounds to
18 minutes lost per day × 5 days = 1.5 hours a week.
Over a 48-week working year: 72 hours — close to two full working weeks.
At $22 an hour, that's $1,584 of unpaid time from a single habitual typing error.
It runs the other way too. Someone entering 7 hours 20 minutes as 7.20 instead of 7.33 loses 8 minutes; someone entering 7 hours 10 minutes as 7.10 rather than 7.17 loses 4. The error is always in the same direction for minute values above the decimal equivalent, and it never announces itself — the number looks plausible, so nobody queries it.
The check takes a second: if the digits after the decimal point are above 59, the entry is definitely wrong. If they look like the minutes you actually worked, they're probably wrong too.
Converting decimal hours back to minutes
To reverse the conversion, multiply the decimal portion by 60. The whole number stays as hours.
This is the sanity check worth running on any timesheet you're approving. Convert the decimal back and ask whether the shift really was that long. A 7.45 entry reverses to 7 h 27 m — and if the shift was actually 7 h 45 m, the discrepancy surfaces immediately.
Common mistakes with decimal time
Reading the decimal as minutes. 7.45 is 7 h 27 m, not 7 h 45 m. Divide minutes by 60 — never just move them after the point.
Rounding each entry before totalling. Round once at the end if you round at all. Rounding five daily entries compounds the error across the week.
Truncating instead of rounding. 0.6666 becomes 0.67, not 0.66. Cutting the digits off rather than rounding them shaves minutes across a full timesheet.
Mixing formats in one sheet. Some rows in hours and minutes, others in decimal, is how totals go wrong unnoticed. Pick one format for the whole sheet.
Assuming rounding is always legal. Under the FLSA rounding must be neutral over time, and several states are stricter. Systematically favouring the employer is not permitted.