Time Difference Calculator
Add or subtract hours, minutes and seconds, or find the gap between two times.
What the Time Difference Calculator does
Time arithmetic works in base 60, not base 10, which is why adding durations by hand goes wrong so often. This converts everything to seconds, does the arithmetic, and converts back.
Formula
Total seconds = Hours × 3600 + Minutes × 60 + SecondsResult = First ± Second, converted back to h:mm:ss
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Operation | one of 2 options | Yes | — |
| Hours | number | Optional | — |
| Minutes | number | Optional | — |
| Seconds | number | Optional | — |
| Hours (second value) | number | Optional | — |
| Minutes (second value) | number | Optional | — |
| Seconds (second value) | number | Optional | — |
How to use it
- Choose Operation.
- Optionally add Hours, Minutes and Seconds.
- Select Calculate.
Worked example
Subtracting 2h 45m 30s from 5h 20m 15s.
- First
- 5:20:15
- Second
- 2:45:30
2h 34m 45s, or 2.579 decimal hours.
Frequently asked questions
Why can I not just subtract the numbers?
Because minutes and seconds roll over at 60, not 100. Subtracting 45 minutes from 20 minutes requires borrowing an hour, exactly as in the calculation above.