Time duration formula
Duration = End − Start (add 24 h if End < Start)
Decimal hours = Hours + Minutes ÷ 60
Decimal hours = Hours + Minutes ÷ 60
Example: From 9:15 AM to 5:45 PM is 8 hours 30 minutes, or 8.5 decimal hours. A night shift from 10:00 PM to 6:30 AM is also 8 hours 30 minutes. Subtracting a 30-minute break leaves 8 hours.
Minutes to decimal hours
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.08 | 35 | 0.58 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 25 | 0.42 | 55 | 0.92 |
| 30 | 0.50 | 60 | 1.00 |
For a whole week of shifts with overtime and pay, use the hours worked calculator.
How to use the calculator
- Enter the start time and the end time. Your browser shows 12-hour or 24-hour format depending on your settings.
- Add any unpaid break in minutes, such as a lunch break.
- Read the duration in hours and minutes, in decimal hours and in total minutes. If the end is earlier than the start, the period is treated as running past midnight.
Worked examples
| Start | End | Break | Duration | Decimal hours |
|---|---|---|---|---|
| 08:00 | 16:30 | 30 min | 8 h 00 min | 8.00 |
| 09:00 | 17:00 | 60 min | 7 h 00 min | 7.00 |
| 07:30 | 15:45 | 15 min | 8 h 00 min | 8.00 |
| 22:00 | 06:30 | 30 min | 8 h 00 min | 8.00 |
| 13:15 | 21:40 | 0 min | 8 h 25 min | 8.42 |
Converting between time formats
There are three common ways to write the same duration, and mixing them up is the most frequent timesheet error:
- Hours and minutes (8 h 30 min) — how people speak about time.
- Clock notation (8:30) — looks like a time of day; 8:30 is not 8.30 hours.
- Decimal hours (8.5) — what payroll and invoicing need. Multiply decimal hours by the hourly rate to get pay.
To go from decimal back to minutes, multiply the decimal part by 60: 7.75 hours = 7 hours + 0.75 × 60 = 7 hours 45 minutes. A typical mistake is reading 7.75 as “7 hours 75 minutes”.
Common uses
- Shift and timesheet totals for hourly workers, including night shifts that cross midnight.
- Billing clients by the hour or in 6-minute (0.1-hour) or 15-minute increments.
- Travel and event planning — how long a flight, drive or meeting takes.
- Sleep tracking — bedtime to wake-up time; 23:15 to 07:00 is 7 hours 45 minutes.
Durations that span more than one day, or that need dates, are easier with the date difference calculator.
Frequently asked questions
How do I calculate hours between two times?
Convert both times to minutes after midnight, subtract, and convert back to hours and minutes. From 9:15 to 17:45 is 1,065 − 555 = 510 minutes = 8 hours 30 minutes.
What if the end time is past midnight?
If the end time is earlier than the start time, the calculator assumes the period crosses midnight and adds 24 hours. 22:00 to 06:30 is 8 hours 30 minutes.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 30 minutes = 0.5 hours, 15 minutes = 0.25, 45 minutes = 0.75 and 20 minutes ≈ 0.33. Payroll systems often need decimal hours.
Does it handle AM/PM?
Your browser shows the time picker in your local format (12-hour or 24-hour). The calculation is identical either way.
How do I add up several time durations?
Convert each one to minutes, add them, then divide by 60. The whole number is hours and the remainder is minutes: 3 h 40 min + 2 h 35 min = 220 + 155 = 375 minutes = 6 h 15 min.
Does the calculator account for daylight saving time?
No. It measures clock time on the same night. On the night clocks change, a shift crossing the change is one hour shorter or longer in real time.