Your timesheet says you worked 7.5 hours and your payroll shows 7 hours 30 minutes. A movie runs 2 h 15 min and you need the seconds for a calculation. And when booking an international flight, is 3 PM 15:00 or 03:00?
Time uses the sexagesimal system (base 60), not decimal. That's why 1.5 hours are not 1 hour 50 minutes, but 1 hour 30 minutes. Mastering these conversions saves you mistakes at work, when traveling and in daily life.
The base rules of time
- 1 minute = 60 seconds
- 1 hour = 60 minutes = 3600 seconds
- 1 day = 24 hours = 1440 minutes
- 1 week = 7 days
Quick time conversion table
| From | To | Factor |
|---|---|---|
| 1 hour | minutes | × 60 |
| 1 minute | seconds | × 60 |
| 1 hour | seconds | × 3600 |
| 1 day | hours | × 24 |
| 1 week | days | × 7 |
| 1 year | days | × 365 (366 in leap years) |
Practical time conversion examples
- 2.5 hours in minutes: 2.5 × 60 = 150 min.
- 90 minutes in hours: 90 ÷ 60 = 1.5 h.
- A 2 h 15 min movie in seconds: 2 × 3600 + 15 × 60 = 8100 s.
- A week in hours: 7 × 24 = 168 h.
Decimal hours at work: the most common case
Many companies log working time in decimal format (7.5 h), but payroll and timesheets are read in hours and minutes. To turn 7.5 hours into hours and minutes: 0.5 × 60 = 30 → 7 h 30 min. And the other way: 8 h 45 min is 8 + 45/60 = 8.75 h.
| Decimal hours | Hours and minutes |
|---|---|
| 0.25 | 15 min |
| 0.5 | 30 min |
| 0.75 | 45 min |
| 1.5 | 1 h 30 min |
| 2.25 | 2 h 15 min |
12-hour and 24-hour formats
To go from 12-hour time to 24-hour time: afternoon hours add 12 (3 PM = 15:00); early morning hours subtract 12 (3 AM = 03:00). Noon is 12:00 and midnight is 00:00. This mistake is typical when booking flights or international meetings: a "3:00 PM" flight departs at 15:00, not 3 in the morning.
Common time conversion mistakes
- Treating hours as decimals: 1.5 h is 90 min, not 1 h 50 min.
- Forgetting that a day has 24 hours when calculating deadlines (a "3-day deadline" is 72 hours, not 36).
- Confusing AM/PM when converting between clock formats.
- Adding minutes directly: 1 h 45 min + 45 min = 2 h 30 min, not 1 h 90 min (and 90 min becomes 1 h 30 min).
FAQ about time conversion
How many seconds are in an hour?
3600 seconds.
How many hours are in a week?
168 hours (7 × 24).
How do I convert 0.25 hours to minutes?
0.25 × 60 = 15 minutes.
How do I convert 2.75 hours to hours and minutes?
0.75 × 60 = 45, so it's 2 h 45 min.
What time is 3 PM in 24-hour format?
15:00.
Convert hours, minutes and seconds without thinking with the unit calculator — sexagesimal time solved in seconds.
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