Time Calculator — Add, Subtract, and Find Time Differences
Add or subtract hours, minutes, and seconds, or find the difference between two times. See also Hours Calculator and Time Duration Calculator.
How the Time Calculator Works
This time calculator performs arithmetic on time values expressed in hours, minutes, and seconds. It converts all inputs to total seconds, performs the addition or subtraction, then converts back to hours:minutes:seconds format. For time differences, it calculates the elapsed time between a start and end time within the same day.
Time Arithmetic Formulas
Total Seconds = hours x 3600 + minutes x 60 + seconds
Hours (decimal) = total_seconds / 3600
HH:MM:SS from seconds: H = floor(sec/3600), M = floor((sec%3600)/60), S = sec%60
12h format: if H > 12 then H-12 PM, if H = 0 then 12 AM
Time Conversion Reference
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 Minute | 60 | 1 | 0.0167 |
| 1 Hour | 3,600 | 60 | 1 |
| 1 Day | 86,400 | 1,440 | 24 |
| 1 Week | 604,800 | 10,080 | 168 |
| 1 Month (avg) | 2,629,746 | 43,829 | 730.5 |
| 1 Year (avg) | 31,556,952 | 525,949 | 8,765.8 |
Frequently Asked Questions
How do I add hours and minutes together?
Enter your start time, select "Add", then enter the hours and minutes to add. The calculator handles overflow automatically (e.g., 45 minutes + 30 minutes = 1 hour 15 minutes).
What is the difference between 12-hour and 24-hour format?
24-hour format runs from 00:00:00 to 23:59:59. 12-hour format uses AM/PM notation where 13:00 becomes 1:00 PM and 00:00 becomes 12:00 AM (midnight).
Can the result exceed 24 hours?
Yes. When adding time values, the result can exceed 24 hours (e.g., 20:00 + 6:00 = 26:00:00). The calculator shows the raw total rather than wrapping to the next day.
How do I calculate time between two clock times?
Use the "Time Difference" mode. Enter the start time and end time, then click Calculate. The result shows the elapsed time in hours, minutes, and seconds.
What does "decimal hours" mean?
Decimal hours express time as a single number. For example, 1 hour 30 minutes = 1.5 hours, and 2 hours 15 minutes = 2.25 hours. This format is commonly used in timesheets and billing.
How do I convert minutes to hours and minutes?
Divide the total minutes by 60. The whole number is hours, and the remainder is minutes. For example, 150 minutes = 2 hours and 30 minutes (150 / 60 = 2 remainder 30).