Add or subtract time values. Calculate elapsed time between two times, convert decimal hours to clock time, convert to military (24-hour) time, and work out speed, distance and time.
Use the Add/Subtract Times tool below for HH:MM:SS arithmetic, the Time Difference tool to find elapsed time between two clock times, and the Time Unit Converter for seconds/minutes/hours/days/weeks conversions. For decimal-hours-to-clock-time (like payroll timesheets) and military time, see the reference tables further down the page.
Enter multiple time values to add or subtract. Format: HH:MM:SS
| Unit | Value |
|---|
| Unit | Seconds | Minutes |
|---|---|---|
| 1 minute | 60 | 1 |
| 1 hour | 3,600 | 60 |
| 1 day | 86,400 | 1,440 |
| 1 week | 604,800 | 10,080 |
| 1 year (365d) | 31,536,000 | 525,600 |
Payroll systems, timesheets and invoicing often express hours as a decimal — 7.75 hours rather than 7 hours 45 minutes — because decimals are easier to sum and multiply by an hourly rate. Converting between the two formats is a common point of confusion: the fractional part of a decimal hour is not the same as minutes, since 0.75 hours is 45 minutes, not 75 minutes.
Military time — also called the 24-hour clock — avoids the AM/PM ambiguity of standard time by numbering hours 00 to 23 continuously through the day. It's standard in aviation, the armed forces, healthcare, logistics and most of the world outside the US, Canada, Australia's everyday speech and a handful of other English-speaking countries.
| Standard (12-hour) | Military (24-hour) |
|---|---|
| 12:00 AM (midnight) | 00:00 |
| 9:00 AM | 09:00 |
| 12:00 PM (noon) | 12:00 |
| 1:00 PM | 13:00 |
| 5:30 PM | 17:30 |
| 11:59 PM | 23:59 |
The classic physics relationship between speed, distance and time rearranges to solve for whichever value is unknown, given the other two.
Biweekly pay periods (every 2 weeks, 26 pay periods a year) are common in Australian casual and shift-based payroll alongside the more typical weekly and fortnightly cycles. To convert a biweekly hours total into a pay figure: add up all shift hours across the 14-day period (in decimal form using the method above), then multiply by the hourly rate.
| Decimal Hours | Hours and Minutes |
|---|---|
| 0.25 hours | 15 minutes |
| 0.5 hours | 30 minutes |
| 0.75 hours | 45 minutes |
| 1.33 hours | 1 hour 20 minutes |
| 2.5 hours | 2 hours 30 minutes |
| 7.75 hours | 7 hours 45 minutes |
Download time depends on file size and connection speed, and the two are commonly given in different units (megabytes for file size, megabits per second for connection speed) which trips people up. Since 1 byte = 8 bits, a connection advertised as "100 Mbps" downloads at roughly 12.5 MB/s, not 100 MB/s.
Beginner:
3 hours 30 minutes (0.5 × 60 = 30).
16:00 (4 + 12).
Advanced:
315 ÷ 4.5 = 70 km/h.
20 ÷ 60 = 0.333, so 8.33 decimal hours.
How do you add times together?
Convert all times to a common unit (seconds or minutes), sum them, then convert back. Example: 2h 45m + 3h 30m = (2×60+45) + (3×60+30) = 165 + 210 = 375 minutes = 6 hours 15 minutes. Alternatively: add minutes (75 minutes = 1h 15m), add hours (5+1=6), result = 6h 15m.
How do I convert decimal hours to hours and minutes?
Multiply the decimal part by 60. Example: 7.75 hours → 7 hours + 0.75×60 = 7 hours 45 minutes. 8.33 hours → 8 hours + 0.33×60 = 8 hours 20 minutes. Useful for converting payroll decimal hours back to clock time.
How do I calculate the time between two times?
Enter a start time and end time and this time calculator works out the elapsed time between them in hours and minutes. It also adds or subtracts durations, so you can add time to a starting point.
How do I convert to military (24-hour) time?
For AM times, military time matches standard time except midnight (12:00 AM becomes 00:00). For PM times, add 12 to the hour — 5:30 PM becomes 17:30 — except 12:00 PM (noon), which stays 12:00.
How do I calculate speed, distance or time from the other two?
Speed = Distance ÷ Time. Distance = Speed × Time. Time = Distance ÷ Speed. Keep units consistent — for example, kilometres and hours together give speed in km/h.
How long will a file take to download?
Download time (seconds) = file size in MB × 8 ÷ connection speed in Mbps. The ×8 converts megabytes to megabits, since internet speeds are advertised in bits, not bytes, per second. Real-world download speeds are usually somewhat below the advertised maximum.