Adding durations means carrying at sixty rather than at a hundred, which is exactly where mental arithmetic slips. 2:45 plus 3:30 is 6h 15m, not 5 hours 75 minutes and not 6.15 of anything. This calculator converts both entries to minutes, adds them, and converts back, so the carry is handled once and correctly.
The finishing time is included because a total on its own rarely answers the real question. If two tasks of 2:45 and 3:30 run back to back from 09:00, the block ends at 15:15 — a figure you would otherwise work out in a second step.
Both entries accept a plain decimal too, so 1.5 is read as one and a half hours and 90m as ninety minutes. Anything the parser cannot read is treated as zero rather than producing a nonsense total, and the result always names how many minutes went into it.
The formula
A- First duration
B- Second duration
T- Combined total in minutes
F- Finishing clock time
How it works, step by step
- Enter the first duration as H:MM, or as a decimal number of hours.
- Enter the second duration the same way.
- Enter the clock time the combined block would start at.
- Read the total, its decimal form and the finishing time.
Worked examples
2:45 plus 3:30
In minutes that is 165 + 210 = 375, which converts back to 6h 15m or 6.25 decimal hours. Starting at 09:00, the block finishes at 15:15.
Two long tasks running past midnight
A 7:20 task and a 5:50 task total 13h 10m. Begun at 14:00 they finish at 03:10 the next day, because the sum of 790 minutes exceeds the 600 minutes left in the day.
How to read your score
Frequently asked questions
Why can I not just add the numbers as decimals?
Because 2:45 is not 2.45. The minutes are sixtieths, so 2:45 is 2.75 hours. Adding the written forms gives 6.15, while the correct total is 6.25 hours — a gap of 6 minutes.
Can I enter a decimal instead of H:MM?
Yes. A bare number is read as hours, so 3.5 means three and a half hours. Mixing the two forms in the same calculation is fine.
What happens if the block runs past midnight?
The finishing time wraps around and the extra line says so. The total duration itself is never wrapped, so a 30-hour combined block still reports as 30 hours.
Does it handle more than two durations?
Not on this page. To add a longer list of durations in one go, use the total hours calculator, which accepts a comma-separated list of any length.
Duration addition reference
| First | Second | Total | Decimal hours | Total minutes |
|---|---|---|---|---|
| 0:45 | 0:30 | 1h 15m | 1.25 | 75 |
| 1:20 | 2:50 | 4h 10m | 4.17 | 250 |
| 2:45 | 3:30 | 6h 15m | 6.25 | 375 |
| 3:15 | 4:45 | 8h 00m | 8.00 | 480 |
| 5:40 | 2:35 | 8h 15m | 8.25 | 495 |
| 7:20 | 5:50 | 13h 10m | 13.17 | 790 |
Every total carries at sixty minutes, so minute columns never exceed 59.