**Full name:** hour

**Plural form:** hours

**Symbol:** hr

**Alternate spelling:** hrs

**Category type:** time

**Scale factor:** 3600

The SI base unit for time is the second.

1 second is equal to 0.00027777777777778 hours.

Valid units must be of the **time** type.

You can use this form to select from known units:

The hour was originally defined in Egypt as 1/24 of a day, based on their duo-decimal numbering system (which counted finger joints on each hand).

hours to day

hours to anomalistic month

hours to synodic month

hours to microsecond

hours to Gaussian year

hours to draconic month

hours to hour

hours to century

hours to nanosecond

hours to decade