Two additions and a subtraction
- Durations, one per line
- 1:45:30 2:20:15 - 0:30:00
- Total
- 3 h 35 min 45 s
- Total as H:MM:SS
- 3:35:45
- Decimal hours
- 3.5958 h
Checked against: (6330 + 8415 − 1800) s = 12945 s = 3 h 35 min 45 s; 12945/3600 = 3.5958333…
Time calculator: add and subtract hours and minutes
Add and subtract hours, minutes and seconds from a list of durations, with the total as H:MM:SS, decimal hours, minutes and seconds.
By AdminDrafted with AI writing toolsUpdated Checked examples: 4
Total
3 h 35 min 45 s
Total: 3 h 35 min 45 s
- Total as H:MM:SS
- 3:35:45
- Decimal hours
- 3.5958h
- Total minutes
- 215.75min
- Total seconds
- 12,945s
The 3 entries add up to 3:35:45 (H:MM:SS), which is 3.5958 hours or 215.75 minutes.
Each entry in hours
Line by line
| Line | Entry | Seconds | Running total |
|---|---|---|---|
| 1 | 1:45:30 | 6,330 | 1:45:30 |
| 2 | 2:20:15 | 8,415 | 4:05:45 |
| 3 | - 0:30:00 | −1,800 | 3:35:45 |
How it's calculated S
Convert each entry to seconds
H:MM:SS → 3600 × H + 60 × MM + SS.
Back to hours, minutes and seconds
12,945 s = 3:35:45
Decimal hours
About the time calculator
Each line is converted to seconds (3,600 × hours + 60 × minutes + seconds), lines that start with a minus sign are subtracted, and the sum is turned back into hours, minutes and seconds. Entries can be written as H:MM:SS, H:MM, 2h 15m, 90 min or 1.5 h. The total is a duration, not a time of day, so 23:59:59 plus one second gives 24:00:00 rather than wrapping to midnight.
Typical uses are adding up timesheet entries, video clip lengths, lap splits and flight legs. The default list, 1:45:30 plus 2:20:15 minus 0:30:00, totals 3:35:45, which is 3.5958 decimal hours or 215.75 minutes.
Decimal hours are the total seconds divided by 3,600, the form payroll and invoicing systems usually ask for: 7 hours 45 minutes is 7.75 hours. To find the time between a start and an end time of day, use the hours calculator instead.
How to add and subtract hours and minutes
Add hours to hours and minutes to minutes, then turn each 60 minutes into an hour: 2:40 plus 1:35 is 3 hours 75 minutes, which is 4:15. To subtract, take an hour from the hours column when the minutes run short: 4:15 minus 1:35 becomes 3:75 minus 1:35, or 2:40. Seconds carry into minutes the same way.
For a longer list, convert every entry to seconds, add them, and convert the total back; NIST's time-unit table fixes the minute at 60 seconds and the hour at 3,600. Three video clips of 12 min 35 s, 8 min 50 s and 21 min 15 s are 755 + 530 + 1,275 = 2,560 seconds, or 42 minutes 40 seconds.
How to write durations: H:MM, minutes and units
A colon separates hours from minutes and, optionally, seconds, so a two-part entry means H:MM: 1:30 is 1 hour 30 minutes. Lap splits and video timestamps often use minutes and seconds instead, so write a clip of 1 minute 30 seconds as 0:01:30 or 1m 30s.
| Entry | Meaning | H:MM:SS result |
|---|---|---|
| 1:30 | 1 hour 30 minutes | 1:30:00 |
| 0:01:30 | 1 minute 30 seconds | 0:01:30 |
| 90 | 90 minutes | 1:30:00 |
| 1.5 h | 1.5 hours | 1:30:00 |
| 1.5 | 1.5 minutes | 0:01:30 |
| 2h 15m | 2 hours 15 minutes | 2:15:00 |
| 45 s | 45 seconds | 0:00:45 |
| 1d 2h | 26 hours | 26:00:00 |
The clips above show the trap: typed as 12:35, 8:50 and 21:15, they read as hours and minutes and total 42:40:00, sixty times their real length.
- A number without a unit is minutes.
90and90 minare the same, and1.5is a minute and a half; label decimal hours as1.5 h. - Minutes and seconds after a colon stop at 59.
1:60is rejected; unit labels allow larger values, such as90 min. - A minus sign at the start of a line subtracts the whole line, so
- 1h 30mremoves 90 minutes. - Repeated durations can be multiplied in minutes. Three 90-minute sessions entered as
90*3give 4:30:00, and1/2is half a minute. A labeled entry such as1h*3can't be multiplied.
Carrying past 60 minutes and 24 hours
Carry at exactly 60: 0:00:59 plus 0:00:01 is 0:01:00, and 0:59:59 plus one second is 1:00:00. A duration keeps counting past 24 hours instead of wrapping like a clock, so 20:00 plus 6:30 is 26:30:00, not 2:30, and 1d is a fixed 24 hours.
What a negative total means
A total below zero is a shortfall, not a time on the previous day. 4:00 minus 5:15 gives −1:15:00, meaning 1 hour 15 minutes short, and equal positive and negative entries cancel to 0:00:00.
Decimal hours and rounding
Decimal hours are total minutes ÷ 60, or total seconds ÷ 3,600. 2 hours 20 minutes is 2.3333 hours, which a two-decimal timesheet shows as 2.33.
Round once, at the end. Three entries of 20 minutes make exactly 1 hour, but rounding each to 0.33 first gives 0.99.
Fractional seconds, as in 0:00:59.99 or 59.99 s, stay in the sum. The H:MM:SS form shows at most one decimal place of seconds and cuts off the rest, so that entry reads 0:00:59.9, while the total in seconds keeps 59.99.
Clock times are not durations
A duration such as three hours has no start date or time of day. To find the time between a start and an end time, including overnight shifts and unpaid breaks, use the hours calculator; it also measures dated punches across a daylight-saving change.
For the days between two calendar dates, use the date difference calculator.
Worked examples
Carrying past 24 hours
- Durations, one per line
- 23:59:59 0:00:01
- Total
- 1 d
- Total as H:MM:SS
- 24:00:00
- Decimal hours
- 24 h
Checked against: 86399 + 1 = 86400 s by hand
A negative total
- Durations, one per line
- 1:00 - 2:30
- Total
- −1 h 30 min
- Total as H:MM:SS
- −1:30:00
- Decimal hours
- -1.5 h
Checked against: 3600 − 9000 = −5400 s by hand
Mixed notations
- Durations, one per line
- 90 min 1.5 h 45 s
- Total
- 3 h 45 s
- Total minutes
- 180.75 min
Checked against: 5400 + 5400 + 45 = 10845 s; 10845 / 60 = 180.75 by hand
Questions
How do I add hours and minutes together?
Add the hours and the minutes separately, then carry every 60 minutes into an hour. 1:45 plus 2:20 gives 3 hours and 65 minutes, and 65 minutes is 1 hour 5 minutes, so the total is 4:05. Seconds carry into minutes the same way. Typing each duration on its own line here does the carrying for you.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 15 minutes is 0.25 hours, 45 minutes is 0.75 hours, so 7 hours 45 minutes is 7.75 hours, and 3:35:45 is 12,945 ÷ 3,600 = 3.5958 hours. When a timesheet rounds to two decimals, each 0.01 hour is 36 seconds, so 3.5958 is entered as 3.60.
How do I convert decimal hours back to hours and minutes?
Keep the whole hours and multiply the decimal part by 60 to get minutes. 1.5 hours is 1 hour 30 minutes, 3.6 hours is 3 hours 36 minutes and 0.1 hours is 6 minutes. Type an entry such as 3.6 h on a line here to see it shown as 3:36:00.
How do I subtract one time duration from another?
Start the line with a minus sign. If the minutes to take away are larger, borrow 60 minutes from the hours: 2:10 minus 0:45 becomes 1:70 minus 0:45, which is 1:25. The total can go below zero; 1:00 minus 2:30 gives −1:30:00, an hour and a half short.
How do I add times in Excel without the total resetting at 24 hours?
Excel stores a time as a fraction of a day, so a plain h:mm format wraps after 24 hours and 25 hours shows as 1:00. Format the total cell with the custom format [h]:mm:ss and the square brackets let hours run past 24. To get decimal hours in Excel, multiply the time by 24.
About this calculator
Sources
- ISO 8601-1:2019 — durations and the extended time format hh:mm:ss
- BIPM, The International System of Units (SI), 9th ed. — minute and hour as non-SI units accepted for use with the SI
Checked against references
This calculator includes 4 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.