Convert hours, minutes, and seconds to decimal hours and reduced fractions, or convert decimal and fractional hours back to HH:MM:SS.
- 100-Minute Clock Calculator
- Tenth of an Hour Calculator
- Hours to Decimal Calculator
- Decimals to Time Calculator
- Subtract Time Calculator
- All Unit Converters
Fraction of an Hour Formula
Select one of three conversions: time to decimal hours, decimal hours to time, or fractional hours to time. Decimal and fraction inputs are rounded to the nearest whole second for HH:MM:SS; the decimal display precision does not change that conversion.
Time to decimal hours:
Decimal hours to time:
Variables:
- H = whole hours
- M = minutes (0 to 59)
- S = seconds (0 to 59)
- D = decimal hours
The “Time to decimal” mode adds hours, minutes, and seconds after converting each to hours, then reports decimal and reduced fractional hours. The “Decimal to time” mode multiplies decimal hours by 3600, rounds to the nearest second, and splits the duration into hours, minutes and seconds. The fraction mode first divides numerator by denominator. A reduced input fraction can differ from the fraction after whole hours when second rounding is needed.
Common Fractions of an Hour
Use this table to convert minutes to a fraction or decimal hour at a glance.
| Minutes | Fraction of hour | Decimal hour |
|---|---|---|
| 5 | 1/12 | 0.0833 |
| 6 | 1/10 | 0.10 |
| 10 | 1/6 | 0.1667 |
| 12 | 1/5 | 0.20 |
| 15 | 1/4 | 0.25 |
| 20 | 1/3 | 0.3333 |
| 30 | 1/2 | 0.50 |
| 40 | 2/3 | 0.6667 |
| 45 | 3/4 | 0.75 |
| 50 | 5/6 | 0.8333 |
Payroll systems usually round to two decimal places. The table below shows how a partial hour gets recorded on a timesheet.
| Time worked | Payroll decimal |
|---|---|
| 7 hr 30 min | 7.50 |
| 8 hr 15 min | 8.25 |
| 8 hr 45 min | 8.75 |
| 9 hr 20 min | 9.33 |
| 10 hr 6 min | 10.10 |
Example Problems
Example 1. You worked 6 hours and 45 minutes. What fraction of an hour is the leftover, and what is the decimal total?
Decimal hours = 6 + 45/60 = 6 + 0.75 = 6.75 hours. The 45 minutes is 45/60, which reduces to 3/4 of an hour.
Example 2. A log file shows 2.4 hours. Convert that back to hours, minutes, and seconds.
Total seconds = 2.4 × 3600 = 8,640 seconds. That splits into 2 hours, 24 minutes, 0 seconds. The fraction after the whole hours is 24/60, or 2/5 of an hour.
FAQ
How do you turn minutes into a fraction of an hour?
Put the minutes over 60 and reduce. For 20 minutes, that is 20/60 = 1/3.
How do you turn minutes into a decimal hour?
Divide minutes by 60. For 20 minutes, that is 20 ÷ 60 = 0.3333 hours.
Why does my payroll decimal not match the exact value?
Payroll usually rounds to the nearest 0.01 hour, which is 36 seconds. A value like 9 hr 20 min is exactly 9.3333, but it shows as 9.33 on a timesheet.
What does the “fraction after whole hours” line mean?
It is the leftover time expressed as a reduced fraction of one hour. For 1 hour 30 minutes, the whole hour is 1 and the leftover is 30/60 = 1/2.
