How to Convert HH:MM:SS to Decimal Hours
While we use the hours, minutes, and seconds format (HH:MM:SS) every day, it's not very friendly for mathematical calculations. If you've ever tried to add up hours on a timesheet or analyze time data in a spreadsheet, you know the frustration. Converting time into a decimal format—like 1.5 hours instead of 1 hour and 30 minutes—makes these calculations simple.
I built this tool to be a two-way converter, allowing you to easily switch between standard time and decimal time for hours, minutes, or seconds.
How to Use This Time to Decimal Calculator
How the Conversion Works
The math is based on the simple relationships between time units:
- 1 hour = 60 minutes
- 1 minute = 60 seconds
Time to Decimal
To convert a standard time to a decimal, we convert everything to a common unit. For example, to get decimal hours:
Decimal Hours = Hours + (Minutes / 60) + (Seconds / 3600)
Decimal to Time
To convert a decimal value back to HH:MM:SS format, we do the reverse:
Hours:The whole number part of the decimal value.Minutes:The decimal part multiplied by 60.Seconds:The new decimal part from the minutes calculation multiplied by 60.
My calculator handles all these steps for you instantly.
Minutes to Decimal Conversion Chart
Because you divide minutes by 60, the same values come up again and again on timesheets. Use this quick reference to convert minutes to decimal hours at a glance (rounded to three decimals):
| Minutes | Decimal hours | Minutes | Decimal hours |
|---|---|---|---|
| 5 min | 0.083 | 35 min | 0.583 |
| 10 min | 0.167 | 40 min | 0.667 |
| 15 min | 0.25 | 45 min | 0.75 |
| 20 min | 0.333 | 50 min | 0.833 |
| 25 min | 0.417 | 55 min | 0.917 |
| 30 min | 0.5 | 60 min | 1.0 |
For any value in between, just divide the minutes by 60 — for example, 45 minutes ÷ 60 = 0.75 hours. The calculator above also converts seconds and works in both directions (decimal back to HH:MM:SS).