How to calculate time duration
Subtract the start time from the end time. If the minutes don't subtract cleanly, borrow 60 minutes from the hours. Convert both times to 24-hour format to avoid AM/PM confusion.
Example: 9:15 AM to 5:40 PM
- Convert to 24-hr: 09:15 to 17:40
- Subtract minutes: 40 − 15 = 25 min
- Subtract hours: 17 − 9 = 8 hours
- Result: 8 hours 25 minutes (= 8.42 decimal hours)
Time duration formula
duration = end time − start time
If end < start, add 24 hours to end (crosses midnight)
Midnight handling: if the end time appears earlier than the start time (e.g., 10 PM to 6 AM), add 24 hours to the end. Example: 22:00 to 06:00 → add 24 → 30:00 − 22:00 = 8 hours. If the end is on the next day but later on the clock (09:00 to 17:30 the next day), tick the next-day box and the calculator adds the 24 hours for you.
For conversions between units (SI definitions, NIST SP 330): 1 minute = 60 seconds, 1 hour = 60 minutes = 3,600 seconds, 1 day = 24 hours = 1,440 minutes = 86,400 seconds.
Common time durations
| Event | H:M | Minutes | Seconds |
|---|---|---|---|
| Half an hour | 0:30 | 30 | 1,800 |
| 8-hour shift | 8:00 | 480 | 28,800 |
| 40-hour work week | 40:00 | 2,400 | 144,000 |
| Full day | 24:00 | 1,440 | 86,400 |
| Full week | 168:00 | 10,080 | 604,800 |
Decimal time conversion
Timesheets that multiply hours by a pay rate need decimal hours rather than hours:minutes. To convert: decimal hours = hours + (minutes ÷ 60).
| Minutes | Decimal hours |
|---|---|
| 15 min | 0.25 |
| 30 min | 0.50 |
| 45 min | 0.75 |
| 5 min | 0.08 |
| 10 min | 0.17 |
| 20 min | 0.33 |
| 25 min | 0.42 |
| 40 min | 0.67 |
| 50 min | 0.83 |
| 55 min | 0.92 |
Time zones and duration
This calculator assumes both times are in the same time zone. For cross-timezone durations, convert both times to UTC first, then subtract. A 3 PM ET departure and 6 PM PT arrival (on the same day) is actually a 6-hour flight, not 3 hours, ET is 3 hours ahead of PT, so 3 PM ET = 12 PM PT, and 12 PM to 6 PM = 6 hours.
Time duration for payroll
For hourly employees, time duration directly determines pay. The standard workflow:
- Calculate clock-in to clock-out duration for each day.
- Subtract unpaid breaks, such as a lunch break.
- Convert to decimal hours (e.g., 7h 30m = 7.5).
- Multiply by hourly rate for daily gross pay.
- Sum the days for the pay period.
- Apply overtime: under the federal Fair Labor Standards Act, covered non-exempt employees must get at least 1.5× their regular rate for hours over 40 in a workweek (U.S. Department of Labor).
Use our Salary to Hourly Calculator to convert between pay structures, or the Salary Calculator for a full take-home pay estimate.
Frequently asked questions
How do I calculate hours between two times?
Put both times on a 24-hour clock and take the start from the end, minutes first. From 9:30 AM to 5:45 PM: 17:45 − 09:30 gives 45 − 30 = 15 minutes and 17 − 9 = 8 hours, so 8 hours 15 minutes (8.25 in decimal hours). When the end minutes are smaller, borrow 60 from the hours: 5:15 − 2:45 becomes 4:75 − 2:45 = 2 hours 30 minutes.
How do I convert hours and minutes to decimal?
Minutes ÷ 60, added to the whole hours. 8 hours 30 minutes is 8 + 30/60 = 8.50; 7 h 15 min is 7.25; 6 h 45 min is 6.75. Worth memorising: 15 min = 0.25, 30 min = 0.50, 45 min = 0.75. A timesheet that multiplies hours by a pay rate needs this form.
How do I calculate hours worked for payroll?
Work out each day's clock-in to clock-out time, take off any unpaid break, and convert to decimal hours. Clocking 8:00 AM to 5:00 PM with a 30-minute unpaid lunch is 9 − 0.5 = 8.5 hours; at an example rate of $20 an hour that is $170 before deductions. Add up the days for the pay period. Federal law (the Fair Labor Standards Act) requires covered, non-exempt employees to be paid at least one and a half times their regular rate for hours over 40 in a workweek, per the Department of Labor.
How many minutes are in X hours?
Hours × 60: 1 hour = 60 min, 2 hours = 120 min, 3 hours = 180 min, 8 hours = 480 min, 24 hours = 1,440 min, and a 168-hour week is 10,080 min. Half hours work the same way: 1.5 h = 90 min, 7.5 h = 450 min. Going the other way, divide by 60: 500 min ÷ 60 = 8.33 hours, or 8 hours 20 minutes.
How do I calculate time across midnight?
Add 24 hours to the end time before subtracting. A 10:00 PM to 6:00 AM shift is 22:00 to 30:00 (6:00 + 24), which is 8 hours. The calculator above does this on its own whenever the end time is earlier than the start, and the next-day box adds the 24 hours when the end is later in the clock but on the following day.
What is elapsed time?
It is how long something took: the gap between a start and a finish. A race that starts at 9:00 AM and ends at 10:35 AM has an elapsed time of 1 hour 35 minutes. It is always a length of time, so it is never negative.
How do I add hours and minutes?
Add the minutes together and the hours together, then carry every 60 minutes into an hour. 2 h 45 min + 1 h 30 min: 45 + 30 = 75 min, which is 1 h 15 min, and 2 + 1 + 1 = 4 h, so 4 hours 15 minutes. In decimals it is 2.75 + 1.5 = 4.25, the same answer.
How do I subtract time?
Take minutes from minutes and hours from hours, borrowing 60 minutes when needed. 5 h 20 min − 2 h 45 min: 20 − 45 won't go, so rewrite 5 h 20 min as 4 h 80 min; 80 − 45 = 35 and 4 − 2 = 2, giving 2 hours 35 minutes. It is ordinary borrowing in base 60.
How many hours is 9am to 5pm?
8 hours: 17:00 − 09:00. Take off a 30-minute unpaid lunch and it is 7.5 hours paid; an hour's lunch leaves 7. Five such days with a half-hour lunch come to 37.5 hours, not 40.
How do I convert minutes to hours?
Divide by 60: 30 min = 0.5 h, 90 min = 1.5 h, 120 min = 2 h, 1,440 min = 24 h. For hours and minutes instead of a decimal, keep the whole hours and turn the remainder back into minutes: 500 min is 8 remainder 20, so 8 hours 20 minutes. The Convert tab above works in both directions.