Hours Calculator
Add or subtract hours and minutes · Convert decimal hours to H:MM and back
Quick answer: 2 hours 30 minutes + 1 hour 45 minutes = 4 hours 15 minutes (4.25 decimal hours). Use the calculator below to add multiple time values or convert formats.
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Decimal hours conversion reference
Decimal Hours Conversion Table
| Minutes | Decimal Hours | Common use |
|---|---|---|
| 5 min | 0.0833 | Short task billing |
| 10 min | 0.1667 | 6-minute billing increment (legal) |
| 15 min | 0.25 | Quarter hour — payroll |
| 20 min | 0.3333 | Third of an hour |
| 30 min | 0.5 | Half hour |
| 45 min | 0.75 | Three-quarter hour |
| 1h 30m | 1.5 | Standard session length |
| 1h 45m | 1.75 | Extended session |
| 2h 30m | 2.5 | Half-day project |
| 7h 30m | 7.5 | 9-5 with 30-min lunch |
24-hour vs 12-hour clock by country
Frequently Asked Questions
How do legal billing increments work?
Law firms and consultants typically bill in 6-minute increments (0.1 hour). This means 7 minutes is billed as 0.2 hours (12 minutes), 13 minutes as 0.3 hours, and so on. The 6-minute increment divides an hour into exactly 10 billable units, simplifying calculations.
How do I add hours that total over 24?
This calculator supports totals beyond 24 hours — useful for multi-day project tracking or timesheets. The result shows total hours (e.g. 31h 15m) rather than rolling over to a new day. For time-of-day calculations, use the Time Calculator instead.
Why does my payslip show decimal hours?
Payroll software uses decimal hours because they are easier to multiply by an hourly rate. 7.5 hours x £15/hr = £112.50. With H:MM you would need to convert first: 7:30 / 60 = 7.5 hours. Most payroll systems round to 2 decimal places.