WhenMathDecimal Hours Converter
Convert a clock duration like 7 hours 30 minutes to decimal hours (7.5), or a decimal figure like 7.25 back to hours and minutes (7h 15m). Works in either direction from the same page.
Worked example
7 hours 20 minutes converts to decimal as 7 + 20/60 = 7.333333..., a repeating decimal. The calculator shows it rounded to 6 places (7.333333) and names it as repeating rather than implying that figure is exact. Going the other way, 7.25 decimal hours converts to 7 whole hours plus 0.25 x 60 = 15 minutes, giving 7h 15m exactly, since 0.25 terminates cleanly in base 10.
Why some decimals repeat
A fraction of an hour only converts to a terminating decimal if, in lowest terms, its denominator has no prime factors other than 2 and 5. 20 minutes is 20/60 = 1/3 of an hour, and 3 is neither 2 nor 5, so it never terminates. 15 minutes is 15/60 = 1/4, and 4 is a power of 2, so it terminates exactly.
Limitations
This is a unit conversion only; it does not apply any rounding your employer or timesheet system might use for payroll.
Frequently asked questions
- Why isn't 7h20m exactly 7.33?
- 7.33 is a rounded approximation; the exact value repeats forever (7.3333...). The calculator shows the rounding it applied rather than hiding it.
- Can I convert a negative duration?
- Yes, check "Negative" when converting from hours/minutes/seconds, or enter a negative decimal directly.