Decimal Hours
Decimal hours express a length of time as a single number, where the part after the separator is a fraction of an hour rather than a count of minutes. Seven hours and thirty minutes is 7.5 decimal hours, not 7.30. Payroll and billing systems work in this format because an hourly rate can be multiplied by it directly.
Why Payroll Uses the Format
An hourly rate is money per hour, so the hours have to be a single number before the multiplication means anything. 7:30 is not a number, it is two numbers with a separator between them. Converting it to 7.5 first turns the pay calculation into ordinary arithmetic, which is why exports aimed at payroll almost always offer this format.
Converting Minutes to Decimals
Divide the minutes by 60. The values worth knowing by heart are:
- 6 minutes is 0.1
- 15 minutes is 0.25
- 20 minutes is 0.333, repeating
- 30 minutes is 0.5
- 45 minutes is 0.75
- 50 minutes is 0.833, repeating
Going the other way, multiply the fraction by 60. Half an hour is 0.5, and 0.4 hours is 24 minutes rather than 40.
The Mistake That Costs Money
The frequent error is reading 7.30 as seven hours and thirty minutes. It is seven hours and eighteen minutes, because 0.30 of an hour is 18 minutes. Twelve minutes go missing from that single entry, and across a twenty day month the same slip loses four hours of paid or billed work.
The reverse mistake is writing 7.30 when 7.5 was meant, which quietly underpays the person who worked the time.
Repeating Decimals and Rounding
Twenty minutes is one third of an hour and has no exact decimal, so a system has to store something like 0.33 or 0.3333. Rounding to two places can be off by up to 0.005 hours, which is 18 seconds per entry. That is invisible on one day and visible on an annual total, which is why hours are best stored as recorded time and converted only when they are reported.
Decimal Hours in Sandtime.io
Duration fields accept decimal input directly, so typing 8.5 records eight hours and thirty minutes. A comma works exactly like a point, so 8,5 is the same entry, which matters wherever the comma is the usual decimal separator. Units can also be named, as in 8.5h or 10.5m.
If you only need the arithmetic, the free hours to decimal converter turns hours and minutes into decimal hours and back without an account.
Related Terms
Decimal hours are how a timesheet turns into pay, so they sit next to the hourly rate that multiplies them and the gross pay that results. They interact with time rounding, which decides what the number is before it is converted, and with billable hours when the same figure reaches an invoice.