Time Calculator

Three time tools: duration arithmetic, time between two clock times, and a clock-time adder.

Add or subtract durations

Result4 h 15 min
As h:mm:ss
4:15:00
In decimal hours
4.25
In minutes
255
In seconds
15,300
In days, hours and minutes
4 h 15 min

Working

  1. 2:45:00 + 1:30:00 = 4:15:00

Time between two clock times

12-hour (9:15 AM) or 24-hour (21:15).

Time between8 h 25 min
As h:mm:ss
8:25:00
In decimal hours
8.416667
In minutes
505

Add or subtract time from a clock time

Resulting time2:15 AM (02:15)
Day
1 day later

Time arithmetic is base 60

Minutes and seconds carry at 60, not 100. Adding 2 h 45 min and 1 h 30 min gives 3 h 75 min, which becomes 4 h 15 min. The calculators convert everything to seconds, do the arithmetic, and convert back.

Worked example

Shift from 9:15 AM to 5:40 PM

  1. Convert to 24-hour: 09:15 and 17:40
  2. 17:40 − 09:15 = 8 h 25 min
  3. In decimal hours: 8 + 25 ÷ 60 = 8.4167

The shift lasts 8 h 25 min (8.42 decimal hours).

Crossing midnight

If the end time is earlier than the start time, the calculator assumes it is on the next day: 10:00 PM to 6:00 AM is 8 hours. For spans longer than 24 hours, use the date difference calculator.