Decimal hours express time as a fraction of one hour rather than breaking it into hours and minutes. 1 decimal hour = 60 minutes, so 0.5 = 30 minutes, 0.25 = 15 minutes, and 0.1 = 6 minutes. Timesheets, payroll systems, and invoices commonly use decimal hours because decimal arithmetic is simpler than sexagesimal (base-60) arithmetic.
The formula
decimal = hours + (minutes / 60)
minutes = round(decimal_fraction × 60)
hours = floor(decimal)
The converter rounds minutes to the nearest whole minute. For exact timesheet work, be aware that rounding 0.01 decimal hours = 0.6 minutes ≈ 1 minute (rounded up).
Practical examples
Example 1 — Timesheet entry
You worked 2 hours 45 minutes on a project. Your timesheet requires decimal hours.
45 ÷ 60 = 0.75 → 2.75 hours
Example 2 — Invoice calculation
An invoice charges £80/hour. You worked 3 hours 20 minutes.
20 ÷ 60 ≈ 0.333 → 3.333 hours × £80 = £266.67
Example 3 — Meeting duration
A meeting ran from 9:15 AM to 11:40 AM. Duration = 2 hours 25 minutes.
25 ÷ 60 ≈ 0.417 → 2.417 decimal hours
Common mistakes
Treating 2.5 hours as 2 hours 50 minutes. The decimal represents a fraction of an hour, not a time display. 2.5 hours = 2 hours 30 minutes, not 2 hours 50 minutes.
Adding times in decimal without converting first. If you tracked 1:30 + 2:45, convert both: 1.5 + 2.75 = 4.25 hours (= 4 hours 15 minutes). Never add 1.30 + 2.45 = 3.75 directly from clock times.
Confusing 0.1 with 10 minutes. 0.1 decimal hours = 6 minutes. 10 minutes = 0.167 decimal hours. Use the converter to check unfamiliar fractions.
International and regional variations
| Context | Standard | Example |
|---|---|---|
| US payroll / timesheets | Decimal hours (tenths or hundredths) | 7.5 hours per day |
| UK legal billing | 6-minute units (0.1 hour each) | 1 hour = 10 units of 6 min |
| Scientific / engineering | Decimal hours or seconds | Elapsed time = 3.667 h |
| Aviation | Decimal hours for flight logs | Block time = 1.8 h |
Quick reference — common minute-to-decimal conversions
| Minutes | Decimal hours |
|---|---|
| 5 min | 0.083 |
| 6 min | 0.1 |
| 10 min | 0.167 |
| 15 min | 0.25 |
| 20 min | 0.333 |
| 30 min | 0.5 |
| 45 min | 0.75 |
| 50 min | 0.833 |