Elapsed Time Calculator
Calculate time difference between two timestamps in hours, minutes, and seconds.
Supports AM/PM and 24-hour formats with overnight span detection.
Elapsed time is the duration between a start time and an end time. While the concept is simple, calculation requires careful handling of clock rollovers (midnight crossing), different time formats (12-hour vs. 24-hour), and unit conversions between hours, minutes, and seconds.
Basic elapsed time formula:
Elapsed Time = End Time − Start Time
If the result is negative (end time is on the next day):
Elapsed Time = (End Time + 24 hours) − Start Time
Decomposing into components:
Total Seconds = (Hours × 3600) + (Minutes × 60) + Seconds
Elapsed Seconds = End Total Seconds − Start Total Seconds
From elapsed seconds:
Hours = Elapsed Seconds ÷ 3600 (integer part)
Minutes = (Elapsed Seconds mod 3600) ÷ 60
Seconds = Elapsed Seconds mod 60
Worked example — same day: Start: 9:47:23 AM → 9 × 3600 + 47 × 60 + 23 = 35,243 seconds End: 2:15:08 PM → 14 × 3600 + 15 × 60 + 8 = 51,308 seconds Elapsed: 51,308 − 35,243 = 16,065 seconds Decomposed: 16,065 ÷ 3600 = 4 hours, remainder 3465 → 3465 ÷ 60 = 57 minutes, remainder 45 → 45 seconds Result: 4 hours, 57 minutes, 45 seconds
Worked example — midnight crossing: Start: 11:15 PM → 23:15:00 = 83,700 seconds End: 6:45 AM (next day) → 6 × 3600 + 45 × 60 = 24,300 seconds Elapsed: (24,300 + 86,400) − 83,700 = 27,000 seconds = 7 hours, 30 minutes
Common real-world uses:
- Shift work duration calculations
- Race and competition timing
- Cooking and process timers
- Billing (hourly rate × elapsed hours)
- Productivity tracking
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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