Time Calculator
- Updated
- Formula shown
- Free, no sign-up
Results
2 hours and 45 minutes plus 1 hour and 30 minutes is 4 hours and 15 minutes
How to use the time calculator
- Choose Add or subtract durations to combine two lengths of time, or Add to a clock time to find an end time.
- Pick add or subtract.
- Fill in any of days, hours, minutes and seconds. Blank boxes count as zero, and decimals such as 1.5 hours work.
- Read the result. For clock times, the calculator also says whether the answer falls on the same day, the next day or the day before.
Time arithmetic formula
Result = T₁ ± T₂, then split back: days = ⌊T ÷ 86,400⌋, hours = ⌊remainder ÷ 3,600⌋, minutes = ⌊remainder ÷ 60⌋
End time = (start time + T) mod 24 h · day change = ⌊(start time + T) ÷ 24 h⌋
Time is not decimal: there are 60 seconds in a minute, 60 minutes in an hour and 24 hours in a day. The simplest way to avoid carrying mistakes is to convert everything to one unit, do the sum, then convert back. The calculator works in seconds (to the nearest millisecond) and splits the result into days, hours, minutes and seconds. For clock times it wraps around midnight and counts how many times it did, which gives the day change.
Worked examples
Adding durations. 2 hours 45 minutes is 9,900 seconds and 1 hour 30 minutes is 5,400 seconds. Together they make 15,300 seconds, which is 4 hours and 15 minutes (4:15:00), or 4.25 hours in decimal form.
Adding to a clock time. A flight leaves at 10:00 PM and takes 7 hours 45 minutes (in the same time zone). 10:00 PM is 22 hours after midnight; adding 7.75 hours gives 29.75 hours, which is past 24, so the flight lands at 5:45 AM the next day. If the destination is in another time zone, convert the arrival time with the time zone calculator.
Units of time
| Length | Hours | Minutes | Seconds |
|---|---|---|---|
| 1 minute | 0.0167 | 1 | 60 |
| 1 hour | 1 | 60 | 3,600 |
| 1 day | 24 | 1,440 | 86,400 |
| 1 week | 168 | 10,080 | 604,800 |
| 30 days | 720 | 43,200 | 2,592,000 |
| 365 days | 8,760 | 525,600 | 31,536,000 |
End times from 10:00 PM
Overnight sums are where mental arithmetic usually slips. These were worked out with the calculator, starting at 10:00 PM.
| Length (h:mm) | Ends at | Day |
|---|---|---|
| 1:30 | 11:30 PM | Same day |
| 2:00 | 12:00 AM | Next day |
| 4:15 | 2:15 AM | Next day |
| 7:45 | 5:45 AM | Next day |
| 9:00 | 7:00 AM | Next day |
| 12:30 | 10:30 AM | Next day |
| 26:00 | 12:00 AM | +2 days |
Tips and common mistakes
- Don't treat minutes as decimals. 1:30 is one and a half hours, not 1.3 hours. Convert with minutes ÷ 60: 1 h 30 min = 1.5 h.
- 12 AM is midnight and 12 PM is noon. Adding 2 hours to 11:00 PM gives 1:00 AM on the next day.
- Daylight saving changes are not included. On the night clocks go forward or back, the real end time can differ by an hour.
- For time between two clock readings, such as a work shift, the hours calculator is quicker, and the time card calculator totals a whole week.
To measure the time between two dates and times, for example from a booking to an appointment, use the time duration calculator.
Frequently asked questions
How do you add hours and minutes?
Add the hours and the minutes separately, then turn every 60 minutes into an hour. 2 hours 45 minutes plus 1 hour 30 minutes is 3 hours and 75 minutes, and 75 minutes is 1 hour 15 minutes, so the total is 4 hours 15 minutes (4:15).
How do you subtract hours and minutes?
Subtract the minutes first, borrowing 60 minutes from the hours if you need to. 5 hours 10 minutes minus 2 hours 45 minutes: borrow an hour to make 4 hours 70 minutes, then 70 − 45 = 25 minutes and 4 − 2 = 2 hours, giving 2 hours 25 minutes.
What time is it 7 hours 45 minutes after 10 PM?
5:45 AM the next day. From 10:00 PM, 2 hours reaches midnight, and the remaining 5 hours 45 minutes takes you to 5:45 AM. Choose "Add to a clock time" and the calculator shows the new time and whether it is the same day, the next day or later.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 4 hours 15 minutes is 255 minutes, and 255 ÷ 60 = 4.25 hours. Going the other way, multiply the decimal part by 60: 0.25 hours × 60 = 15 minutes. The calculator shows each result in days, hours, minutes and seconds.
Can I enter decimals such as 1.5 hours?
Yes. Any box accepts decimals, and the calculator converts everything to seconds before adding. 1.5 hours is 1 hour 30 minutes, and 0.25 minutes is 15 seconds, so 1.5 hours plus 0.25 minutes is 1:30:15.