The phrase "how many hours is" is incomplete on its own and usually requires a specific context or period of time to provide a meaningful answer. Commonly, it is used to ask for the duration between two times, like "how many hours is 9 AM to 5 PM," which is 8 hours. It can also ask for the number of hours in larger time units:

• A day has 24 hours.
• A week has 168 hours (7 days x 24 hours).
• A month averages about 730.5 hours but varies by month.
• A year has 8,760 hours in a non-leap year and 8,784 hours in a leap year.

For more specific questions about hours from one time to another or hours in different contexts, the exact times or periods need to be specified.