Time Calculator
Add, subtract, multiply, or divide time. Calculate differences between times and convert between time units.
Add or Subtract Time
Multiply or Divide Time
Calculate Time Difference
Convert Time Units
How to Calculate Time
Adding Time
Add seconds first, carrying over 60+ seconds as minutes. Then add minutes, carrying 60+ as hours. Then add hours, carrying 24+ as days. Finally add days.
Subtracting Time
Subtract from the smallest unit up. If a unit is too small, borrow from the next larger unit: 1 minute = 60 seconds, 1 hour = 60 minutes, 1 day = 24 hours.
Multiplying & Dividing
Convert the time to total seconds, multiply or divide by the factor, then convert back to days, hours, minutes, and seconds.
Duration vs. Clock Time
A duration is a span of time with no upper limit. Clock time is a point in a day (0-23 hours). This calculator supports both.
Decimal Time
Decimal hours are useful for timesheets. For example, 1.5 hours = 1 hour 30 minutes and 0.25 hours = 15 minutes.
Approximate Units
Months and years vary in length. This calculator uses average values: 1 month = 30.437 days and 1 year = 365.25 days (accounting for leap years).
Time Conversion Reference
| Unit | Equivalent | In Seconds |
|---|---|---|
| 1 Minute | 60 Seconds | 60 |
| 1 Hour | 60 Minutes | 3,600 |
| 1 Day | 24 Hours | 86,400 |
| 1 Week | 7 Days | 604,800 |
| 1 Month (avg) | ~30.437 Days | ~2,629,756 |
| 1 Year (avg) | ~365.25 Days | ~31,557,600 |
Frequently Asked Questions
To add time, start by adding the seconds. If the total seconds exceed 60, carry over the extra to minutes (e.g., 45s + 30s = 75s = 1m 15s). Then add the minutes and carry over any excess above 60 to hours. Add the hours and carry over any excess above 24 to days. Finally, add the days. For example, 2d 21h 45m 39s + 5d 10h 45m 22s: seconds 39+22=61 (1m 1s carry), minutes 45+45+1=91 (1h 31m carry), hours 21+10+1=32 (1d 8h carry), days 2+5+1=8. Result: 8d 8h 31m 1s.
To subtract time, start with the seconds. If the first value is smaller, borrow 1 minute (60 seconds) from the minutes column. Then subtract minutes, borrowing from hours if needed (1 hour = 60 minutes). Then subtract hours, borrowing from days if needed (1 day = 24 hours). Finally subtract days. For example, 5d 10h 15m 20s - 2d 18h 45m 50s: seconds 20-50 requires borrowing (80-50=30s), minutes 14-45 requires borrowing (74-45=29m), hours 9-18 requires borrowing (33-18=15h), days 4-2=2. Result: 2d 15h 29m 30s.
To multiply time by a number, first convert the entire time duration to seconds. Then multiply by the factor. Convert the result back to days, hours, minutes, and seconds by dividing successively by 86,400 (seconds per day), 3,600 (seconds per hour), and 60 (seconds per minute). Division works the same way: convert to total seconds, divide by the number, then convert back. For example, 2d 10h 32m 16s times 5: total seconds = 210,736. Multiply by 5 = 1,053,680 seconds = 12 days 4 hours 41 minutes 20 seconds.
A time duration represents a length or span of time, such as "3 hours 45 minutes." It can exceed 24 hours and has no upper limit. A clock time represents a specific point in the day, such as "2:30 PM" or "14:30" in 24-hour format, and is always between 00:00:00 and 23:59:59. When adding durations, results can be any value. When calculating the difference between clock times, you are finding the duration between two points in a day.
There are exactly 86,400 seconds in a day. This is calculated as 24 hours x 60 minutes x 60 seconds = 86,400 seconds. Similarly, there are 1,440 minutes in a day (24 x 60), 3,600 seconds in an hour (60 x 60), and 604,800 seconds in a week (86,400 x 7). These conversion factors are fundamental to time arithmetic.