Add Hours & Minutes
Add a duration in hours and minutes to a 24-hour start time and get the finish time plus a day offset, with a worked example that crosses midnight.
Results
Result time
- Day offset
- 0
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Formula / how it works
Total minutes = (start hour × 60 + start minute) + (hours added × 60 + minutes added). Finish time = total minutes mod 1,440. Day offset = floor(total minutes ÷ 1,440).
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Adding a duration to a clock time sounds easy until minutes go past 59 or the total passes midnight. This calculator takes a start hour and minute on a 24-hour clock and a number of hours and minutes to add, and returns the finish time along with the number of days later it falls. It is handy for flight and shift schedules, cooking and baking times, work logs and timers. It works on a clock face only and does not know about time zones or daylight saving changes, so for travel across zones add the zone difference separately.
When to use / who it helps
- You want to know when a task starting at a given time will finish.
- You are planning a shift or a long journey.
- You are adding durations in a time sheet.
- You are timing a slow-cooked meal.
- You need to know if the finish time falls on the next day.
How to use
Steps
- Enter the start hour from 0 to 23.
- Enter the start minute from 0 to 59.
- Enter the hours to add.
- Enter the minutes to add; values over 59 are fine.
- Read the finish time and the day offset.
- Convert to 12-hour time if needed.
How to interpret results
- The finish time is on the same 24-hour clock.
- A day offset of 0 means the same day.
- A day offset of 1 means the next day.
- Minutes over 59 roll into hours.
- Time zones and daylight saving are not applied.
Common mistakes & gotchas
- Entering 12-hour times without the 24-hour conversion.
- Treating 90 minutes as 0.9 hours.
- Forgetting the day offset.
- Ignoring time-zone changes on trips.
- Entering an hour above 23.
Worked example
Worked example — 09:30 plus 2 h 45 min, and 22:30 plus 3 h 45 min
- 09:30 is 570 minutes; 2 h 45 min is 165 minutes; the total is 735 minutes.
- 735 ÷ 60 gives 12 hours and 15 minutes, so the finish is 12:15 on the same day.
- 22:30 is 1,350 minutes; 3 h 45 min is 225; the total is 1,575.
- 1,575 − 1,440 = 135 minutes, which is 02:15 with a day offset of 1.
Result: 09:30 plus 2 h 45 min is 12:15; 22:30 plus 3 h 45 min is 02:15 the next day.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
Total minutes = (start hour × 60 + start minute) + (hours added × 60 + minutes added). Finish time = total minutes mod 1,440. Day offset = floor(total minutes ÷ 1,440).
Frequently asked questions
How do I add minutes over 60?
The tool converts them into hours automatically.
What does the day offset mean?
The number of days after the start day on which the result falls.
Does it use a 12-hour clock?
No. Enter hours from 0 to 23.
Does it handle time zones?
No. Add the zone difference separately.
Can I subtract time?
This tool only adds.
How do I convert 90 minutes to hours?
Divide by 60 to get 1.5 hours.