Time Duration Calculator
Add or subtract hours, minutes, and seconds. Calculate time elapsed between two moments, or find a future or past time.
⏰ Time📐 Duration = End Time - Start Time
Start hour (24h)
Start minutes
End hour (24h)
End minutes
Calculation
Hours to add/subtract
Minutes to add/subtract
Please enter valid values.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Time Duration Calculator | Duration = End Time - Start Time | h:mm:ss |
Step-by-Step Examples
Example 1
Work Day Duration
9:30 AM to 5:45 PM.
- Duration: 8 hours 15 minutes = 8.25 decimal hours
✓ 8 hours 15 minutes
Example 2
Add Time
9:00 AM + 3 hours 45 minutes.
- 9:00 + 3h 45m = 12:45 PM
✓ 12:45 PM
Example 3
Subtract Time
17:30 minus 2 hours 15 minutes.
- 17:30 - 2:15 = 15:15 (3:15 PM)
✓ 15:15 / 3:15 PM
Real-World Applications
Workers
Calculate shift length and overtime hours.
Freelancers
Track billable time accurately.
Schedulers
Plan meetings and events with accurate time math.
Athletes
Calculate race pace, training sessions, and rest periods.
Common Mistakes to Avoid
⚠️
AM/PM vs 24-hour confusion
1 PM = 13:00, 5 PM = 17:00, midnight = 0:00, noon = 12:00. Use 24-hour format to avoid AM/PM errors.
⚠️
Cross-midnight shifts
A shift from 10 PM to 6 AM is 8 hours but spans midnight. The calculator adds 24 hours when end time is before start time.
⚠️
Time zone differences in meetings
Always specify time zone when scheduling across regions. Use UTC as a universal reference and convert to local times.
Frequently Asked Questions
Converting decimal hours to minutes? ▾
Multiply the decimal by 60. 8.25 hours = 8 hours + (0.25 x 60) = 8 hours 15 minutes. 7.5 hours = 7 hours 30 minutes.
How many minutes in an hour? ▾
60 minutes. How many seconds in an hour? 3,600 seconds. How many seconds in a day? 86,400 seconds.
Time tracking apps? ▾
Toggl, Clockify, and Harvest are popular time tracking apps for freelancers and teams. They automatically calculate durations, categorize time by project, and export for billing.
What is military time? ▾
The 24-hour clock system used by military, emergency services, international aviation, and many countries. 0000 = midnight, 1200 = noon, 1300 = 1 PM, 2359 = 11:59 PM.
How to calculate overtime? ▾
Sum all hours worked in the workweek (7 consecutive days). Hours over 40 = overtime at 1.5x regular rate under federal law. Some states have daily overtime (over 8 hours/day).