Time Calculator — Add and Subtract Hours, Minutes, Seconds
Add and subtract a list of times like 1:30, 45m or 2h 15m 10s, get the total in h:mm:ss, decimal hours and minutes, and the clock time it ends at.
| Line | Entry | As h:mm:ss | Running total |
|---|---|---|---|
| 1 | 1:30 | 1:30:00 | 1:30:00 |
| 2 | 0:45 | 0:45:00 | 2:15:00 |
| 3 | 2h 15m | 2:15:00 | 4:30:00 |
| 4 | -20m | -0:20:00 | 4:10:00 |
| 5 | 1.5 | 1:30:00 | 5:40:00 |
This time calculator adds up a list of durations — lap times, video clips, billable sessions, flight legs — and subtracts any line that starts with a minus sign. Mix formats freely: 1:30, 2h 15m, 45s, 1d 3h or 1.5 hours. You get the total as h:mm:ss, as days-hours-minutes-seconds, in decimal hours and minutes, and the clock time you finish if you start at a given time.
How to use this tool
- Type or paste one duration per line; start a line with - to subtract it.
- Say whether a two-part time like 4:10 means hours:minutes or minutes:seconds.
- Optionally enter a start clock time to see when you would finish.
- Check the line-by-line table if a total looks wrong — each line shows how it was read.
Formula
Total = Σ (sign × days × 86,400 + hours × 3,600 + minutes × 60 + seconds)
Every line is turned into seconds, added with its sign and turned back into hours, minutes and seconds. A plain number such as 1.5 is read as hours. The end clock time wraps around midnight and shows how many days later (or earlier) it falls.
Example
Adding 1:30, 0:45, 2h 15m, −20m and 1.5 gives 90 + 45 + 135 − 20 + 90 = 340 minutes, which is 5:40:00 or 5.6667 hours. Starting at 09:00 you would finish at 14:40.
Frequently asked questions
Why does 4:10 come out as 4 hours?
Two-part times are ambiguous. Switch "Read a:b as" to minutes:seconds for stopwatch or video times, or write three parts (0:04:10).
Can the total be more than 24 hours?
Yes. The total keeps counting hours (26:03:04), and the days-hours-minutes line shows the same as 1d 2h 3m 4s.
How do I find the time between two clock times instead?
Use the hours calculator, which takes a start and end time and handles shifts across midnight.
Last updated:
Page address with these inputs: https://kakao.mobile/tools/add-time-calculator/
Cite or embed this tool
kakaoCalc. (2026, November 8). Time Calculator — Add and Subtract Hours, Minutes, Seconds. https://kakao.mobile/tools/add-time-calculator/
“Time Calculator — Add and Subtract Hours, Minutes, Seconds.” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/add-time-calculator/.
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