Hours Calculator
Use the calculators below to find the number of hours and minutes between two times. For a full time card, please use the Time Card Calculator.
Hours Between Two Dates
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An hour is most commonly defined as a period of time equal to 60 minutes, where a minute is equal to 60 seconds, and a second has a rigorous scientific definition. There are also 24 hours in a day. Most people read time using either a 12-hour clock or a 24-hour clock.
12-hour clock:
A 12-hour clock uses the numbers 1-12. Depending on the clock being used, most analog clocks or watches may not include an indication of whether the time is in the morning or evening. On digital clocks and watches, "AM" stands for ante meridiem, meaning "before midday," while "PM" stands for post meridiem, or "after noon." By convention, 12 AM denotes midnight, while 12 PM denotes noon. Using the terms "12 midnight" and "12 noon" can remove ambiguity in cases where a person may not be accustomed to conventions.
24-hour clock:
A 24-hour clock typically uses the numbers 0-23, where 00:00 indicates midnight, and a day runs from midnight to midnight over the course of 24 hours. This time format is an international standard, and is often used to avoid the ambiguity resulting from the use of a 12-hour clock. The hours from 0-11 denote what would be the AM hours on a 12-hour clock, while hours 12-23 denote the PM hours of a 12-hour clock. In certain countries, 24-hour time is referred to as military time, since this is the time format used by militaries (and other entities) around the world, where unambiguous time measurement is particularly important.
Hours in different time periods
| Description | Hours |
| Hours in a day | 24 |
| Hours in a week | 168 |
| Hours in a month | 672 for a 28-day month 696 for a 29-day month 720 for a 30-day month 744 for a 31-day month 730.5 on average |
| Hours in a year | 8,760 for a 365-day year 8,784 for a 366-day year 8,766 on average |
| Hours in a decade | 87,648 for a 2-leap-year decade 87,672 for a 3-leap-year decade 87,660 on average |
| Hours in a century | 876,600 |
Frequently Asked Questions
How are overnight hours calculated?
In the first calculator, if the end time is earlier than the start time, it is treated as falling on the following day — so 10:00 PM to 6:00 AM gives 8 hours. For spans across specific dates, use the Hours Between Two Dates calculator.
What time formats can I enter?
Times can be entered as hours and minutes such as 8:30 together with the AM/PM selector, or as a decimal hour such as 8.5 for 8:30. Seconds, if included, are ignored.
What does the decimal hours line mean?
Alongside the hours-and-minutes result, the calculator shows the same span as a decimal number of hours — for example, 1 hour 30 minutes is also shown as 1.5 hours — which is the format often used for timesheets and payroll.