Two ways to use it
- Duration math: leave the start blank. Enter 2 h 45 min and add 1:30:00 to get 4:15:00.
- Clock math: set a start time. Start 10:30 PM, add 3 h 15 min → 1:45 AM the next day.
Carrying minutes and seconds
Time is base 60: 60 seconds make a minute and 60 minutes make an hour. When a column passes 60, carry one to the next column, just like carrying a ten in ordinary addition.
Frequently asked questions
What time will it be in 8 hours?
Set the start to the current time and add 8 hours.
How many minutes is 2 hours 45 minutes?
165 minutes.
Last reviewed 2026-10-14.