Old Faithful erupts at varying intervals from 60 to 110 minutes in length. The Yellowstone National Park staff offers predictions based on past activity; this is so that visitors can plan a visit to the geyser area during an eruption, which lasts between one-and-a-half minutes and five minutes.
The predictions of the park staff are 90 percent accurate, which is how the geyser got its name. Old Faithful is a cone geyser that launches 3,700 to 8,400 gallons of boiling water from heights of 106 to 184 feet. Yellowstone National Park is a hotbed of geyser activity, with 425 active geysers at any one time.