Quick answer
Add seconds to seconds, minutes to minutes, and hours to hours. Carry each group of 60 seconds into minutes and each group of 60 minutes into hours. Keep all the hours, even if the total exceeds 24.
Step by step
- Write the durations in columns with the same unit in each column. Treat 2:45 as 2 hours and 45 minutes when the format is hours:minutes.
- Start with seconds if present. Divide their sum by 60, carry the whole minutes, and keep the leftover seconds.
- Repeat for minutes, then add the hours and any carry. Label the units when you write the result.
Worked examples
Carry minutes
2:45 + 3:30 gives 5 hours and 75 minutes. Carry 60 minutes into hours to get 6:15.
Carry seconds
1:20:45 + 0:10:30 gives 75 seconds, so write 15 seconds and carry one minute. The total is 1:31:15.
Keep hours above 24
13:50 + 13:25 gives 26 hours and 75 minutes, or 27:15. That is 27 hours and 15 minutes of elapsed time.
What to check
For a list that includes deductions, convert each duration to seconds, apply its sign, and convert the signed total back. Apply the minus sign once to the entire final duration.
Related guides
Sources
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