Time Duration Calculator

Time duration is the elapsed interval between two clock times, expressed in hours, minutes, and seconds. On the same calendar day, subtract the earlier time from the later: from 9:30 AM to 2:45 PM, convert to 24-hour format (09:30 and 14:45), subtract: 14:45 − 09:30 = 5 hours 15 minutes = 5.25 hours = 315 minutes = 18,900 seconds.

When the end time is earlier than the start time on the clock, the span crosses midnight. From 10:00 PM to 6:30 AM the next day: add 24 hours to the end time before subtracting. (06:30 + 24:00) − 22:00 = 30:30 − 22:00 = 8 hours 30 minutes. This models overnight shifts, sleep duration, and flights crossing date lines (calendar date adjustments are separate from clock duration).

Decimal hours simplify payroll and billing. 8 hours 30 minutes = 8 + 30/60 = 8.5 hours. At $25/hour, 8.5 hours earns $212.50. Total minutes: 8 × 60 + 30 = 510 minutes. For multiple segments, calculate each duration and sum: a commute of 35 minutes plus an 8-hour workday plus a 40-minute return trip totals 9 hours 15 minutes.

Sleep cycle planning uses duration math: if you fall asleep at 11:15 PM and wake at 7:00 AM, sleep duration is 7:00 + 24:00 − 23:15 = 7 hours 45 minutes (subtracting 15 minutes if "11:15 PM" means lights-out). Five 90-minute sleep cycles need 7.5 hours — adjust bedtime backward from a fixed wake time.

Enter a start time and end time to get the duration in hours, minutes, seconds, and decimal hours. Enable overnight mode when the end time is on the following calendar day. Use for timesheets, travel planning, cooking timers, and sleep tracking.