How to add and subtract time
Time doesn't add like ordinary numbers, because 60 minutes make an hour, not 100. The simplest way is to turn everything into seconds, add or subtract, then convert back.
Seconds = Hours × 3,600 + Minutes × 60 + Seconds
Hours = Total ÷ 3,600 (whole part)
Minutes = (Total remaining ÷ 60) (whole part), Seconds = what's left
Decimal hours = Total seconds ÷ 3,600
Example: 2 h 45 min + 1 h 30 min − 20 min = 9,900 + 5,400 − 1,200 = 14,100 seconds = 3:55:00, or 3.9167 hours.
Minutes to decimal hours
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 6 | 0.1 | 36 | 0.6 |
| 12 | 0.2 | 42 | 0.7 |
| 15 | 0.25 | 45 | 0.75 |
| 18 | 0.3 | 48 | 0.8 |
| 20 | 0.333 | 50 | 0.833 |
| 24 | 0.4 | 54 | 0.9 |
| 30 | 0.5 | 60 | 1.0 |
To total a timesheet from clock-in and clock-out times, use the hours calculator. For the time between two dates, use the date difference calculator.
Frequently asked questions
How do I add hours and minutes?
Add the hours and the minutes separately. If the minutes come to 60 or more, take 60 off and add 1 to the hours. 1:40 + 2:35 = 3:75 = 4:15.
How do I convert minutes to decimal hours?
Divide by 60. 45 minutes is 0.75 hours, so 7 h 45 min is 7.75 hours.
Can the total be negative?
Yes. If you subtract more than you add, the result shows with a minus sign.
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