Decimal Time Converter
Turn 1:30:00 into 1.5 decimal hours, or type 1.75 and get 1:45:00 back — the conversion timesheets, billing, and spreadsheets need. The tool also breaks the value into total minutes and seconds, and, as a curiosity, shows the same instant in French Revolutionary decimal time. It updates live and runs entirely on your device.
Accepts H:MM:SS, H:MM, or a bare number of hours.
e.g. 1.5 = one and a half hours.
How to use the Decimal Time Converter
Type into either box and the other updates instantly. Enter a clock-style value in Time — 1:30:00, 1:30, or just 1.5 hours — and the Decimal hours field shows it as a single number, here 1.5. Or type a decimal such as 2.25 into the decimal field and the time field fills in 2:15:00. Whichever you edit last is the source of truth.
Below the inputs, extra cards restate the same amount as total minutes and total seconds, which is handy when a system wants the duration in one flat unit. A final card shows the value interpreted as a time of day in French Revolutionary decimal time, where the day is split into ten hours of a hundred minutes each — a historical scheme that makes a nice illustration of why our 24×60×60 clock is the way it is.
Everything is computed locally in your browser as you type, so it is instant, works offline, and nothing you enter leaves your device.
Decimal hours and why timesheets use them
Our everyday clock is sexagesimal — based on sixty. An hour has sixty minutes and a minute has sixty seconds, an inheritance from ancient Babylonian astronomy that has proven remarkably durable. It is great for reading the time, but awkward for arithmetic: adding up a week of work logged as 7:45, 8:15, 6:30, and so on means constantly carrying minutes across the sixty boundary. That friction is exactly why payroll, billing, and time-tracking systems prefer decimal hours, where the minutes are expressed as a fraction of an hour. One hour and thirty minutes becomes 1.5; one hour and fifteen minutes becomes 1.25. Now a timesheet is just a column of decimals you can sum and multiply by an hourly rate without any base-60 gymnastics.
The conversion is a simple division and multiplication, but it is the kind of thing that is easy to get subtly wrong by hand. To go from clock time to decimal you add the minutes divided by sixty and the seconds divided by 3,600 to the whole hours: 1:30:00 is 1 + 30/60 = 1.5. To go back, you take the whole-number part as hours, multiply the fractional part by sixty to get minutes, and multiply whatever is left over by sixty again for seconds: 2.25 hours is 2 hours, 0.25 × 60 = 15 minutes, and no seconds. The places people slip up are forgetting that 1.5 hours is 1:30 and not 1:50, and mishandling values like 1.1 hours, which is 1 hour and 6 minutes rather than 1 hour and 10 minutes. A converter removes that ambiguity entirely.
The idea of decimalizing time has a famous historical episode. During the French Revolution, France briefly introduced decimal time: a day divided into ten hours, each hour into a hundred decimal minutes, and each minute into a hundred decimal seconds. It was mathematically elegant — a decimal second is a fixed fraction of the day, and converting between units is just shifting a decimal point — but it required everyone to relearn timekeeping and to buy new clocks, so it was abandoned within a couple of years. The episode is a neat reminder that units survive on inertia and convenience as much as on logic, and that the same instant can be written many different ways. Converting an ordinary time into that ten-hour day, as this tool does for fun, shows just how arbitrary the boundaries of a "minute" or an "hour" really are.
Common use cases
- Timesheets. Convert clocked hours and minutes into decimal hours for payroll entry.
- Billing. Turn a duration into a decimal you can multiply by an hourly rate.
- Spreadsheets. Get a single decimal value to sum or chart instead of HH:MM strings.
- Learning. See the same time as total minutes, total seconds, and decimal time.