Meridian is considered part of the Boise metropolitan area.

Meridian is located at 43°36'51" North, 116°23'56" West (43.614229, -116.398963)^GR1.

According to the United States Census Bureau, the city has a total area of 30.5 km² (11.8 mi²). 30.5 km² (11.8 mi²) of it is land and none of it is covered by water.

As of 2000, there were 34,919 people, 11,829 households, and 9,510 families residing in the city. The population density was 1,143.5/km² (2,962.1/mi²). There were 12,293 housing units at an average density of 402.6/km² (1,042.8/mi²).

There were 11,829 households out of which 49.0% had children under the age of 18 living with them, 68.4% were married couples living together, 8.8% had a female householder with no husband present, and 19.6% were non-families. 14.5% of all households were made up of individuals and 4.3% had someone living alone who was 65 years of age or older. The average household size was 2.93 and the average family size was 3.26.

In the city the population was spread out with 33.7% under the age of 18, 6.9% from 18 to 24, 37.1% from 25 to 44, 15.8% from 45 to 64, and 6.4% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 96.4 males. For every 100 females age 18 and over, there were 93.7 males.

The median income for a household in the city was $53,276, and the median income for a family was $57,077. Males had a median income of $40,360 versus $27,174 for females. The per capita income for the city was $20,150. 5.6% of the population and 4.6% of families were below the poverty line. 7.0% of those under the age of 18 and 7.6% of those 65 and older were living below the poverty line.