How it is worked out
minutes = hours × 60 · seconds = minutes × 60
Why it is done this way
The sexagesimal system comes from Babylon and survives because 60 divides by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30. That is why a third of an hour is exactly twenty minutes, while a third of a hundred minutes would not be a whole number.
Step by step
- Split the hours from the minutes: in 2:45, that is 2 hours and 45 minutes
- Turn the hours into minutes by multiplying by 60: 2 × 60 = 120
- Add the loose minutes: 120 + 45 = 165 minutes
- For seconds, multiply by 60 again: 165 × 60 = 9,900
What is worth knowing
Watch the difference between 2:45 and 2.45. The first is two hours and forty-five minutes; the second is two hours and just under twenty-seven minutes, because 0.45 of an hour is 27 minutes. Mixing them up is the most common mistake when moving a timesheet into a spreadsheet, and it is where underpaid wages come from. This page accepts both, but you have to say which one you are using.