Time Duration Calculator
Calculate the exact duration between two times or add and subtract time intervals easily. Free online time duration calculator for work hours, project planning, and scheduling.
Time Duration Calculation Basics
Time duration calculations measure elapsed time between two points or combine multiple time intervals. This tool handles hours, minutes, seconds, and larger units for accurate scheduling and planning.
Time Arithmetic Formulas
Duration = End Time - Start Time
Total Seconds = (Hours × 3600) + (Minutes × 60) + Seconds
Hours = Total Seconds / 3600
Minutes = (Total Seconds % 3600) / 60
Convert all time values to a common unit before performing calculations. Seconds work well as the base unit for precise arithmetic.
Time Unit Conversion Table
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 Minute | 60 | 1 | 0.0167 |
| 1 Hour | 3,600 | 60 | 1 |
| 1 Day | 86,400 | 1,440 | 24 |
| 1 Week | 604,800 | 10,080 | 168 |
| 1 Month (avg) | 2,629,746 | 43,829 | 730.5 |
| 1 Year | 31,557,600 | 525,960 | 8,766 |
Project Planning Examples
Example 1: Work Hours Calculation
Start: 9:00 AM
End: 5:30 PM
Break: 30 minutes
Result: 8 hours of work time
Example 2: Task Duration Sum
Task A: 2 hours 45 minutes
Task B: 1 hour 30 minutes
Task C: 3 hours 15 minutes
Total: 7 hours 30 minutes
Example 3: Cross-Midnight Duration
Start: 10:00 PM
End: 6:00 AM (next day)
Result: 8 hours
Example 4: Project Timeline
Phase 1: 3 weeks
Phase 2: 2 weeks 4 days
Phase 3: 1 week 3 days
Total: 7 weeks (49 days)
Common Time Calculations
Hours in a Work Week
Standard: 40 hours (8 hours × 5 days)
Extended: 45-50 hours
Part-time: 20-30 hours
Minutes in Common Periods
1 hour: 60 minutes
Half day: 720 minutes
Full day: 1,440 minutes
Work week: 2,400 minutes
Time Zone Differences
EST to PST: 3 hours
EST to GMT: 5 hours
GMT to IST: 5.5 hours
EST to JST: 14 hours
Decimal Time Conversion
1.5 hours = 1 hour 30 minutes
2.25 hours = 2 hours 15 minutes
3.75 hours = 3 hours 45 minutes
0.5 hours = 30 minutes
Frequently Asked Questions
How do you calculate time duration manually?
Convert both times to 24-hour format. Subtract the start time from the end time. If minutes in the end time are less than start minutes, borrow 1 hour (60 minutes). If the result crosses midnight, add 24 hours.
What is the 24-hour time format?
The 24-hour format runs from 00:00 (midnight) to 23:59. Add 12 to PM hours except for 12 PM. 1:00 PM becomes 13:00, 6:00 PM becomes 18:00, and 12:00 AM becomes 00:00.
How do you add time durations?
Add hours together and minutes together separately. If minutes exceed 60, convert excess to hours. For example, 2 hours 45 minutes plus 1 hour 30 minutes equals 4 hours 15 minutes.
How do I calculate overtime hours?
Subtract standard work hours from total hours worked. For a 40-hour work week, any hours beyond 40 count as overtime. Daily overtime rules vary by jurisdiction and employer policy.
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