Pool builders are typically willing to build in-ground pools to the size and shape that best fits the homeowner's budget and available space. Common sizes for rectangular in-ground pools range from 10 feet by 20 feet at the low end to 20 feet by 40 feet at the larger end of the scale.
The pool's primary intended use dictates its ideal size. Pools used mostly by children may be relatively small and shallow, while pools used for recreation and entertainment by adults may need to be toward the bigger end of the range. Fitness pools have their own distinct size requirements; traditional lap pools are often 10 feet wide by 50 feet long.
The appropriate depth of a pool depends largely on who's going to be using the pool and what they're going to be using it for. Pools used by children need to have a roomy shallow end, and the depth in the shallow needs to be no greater than 3 feet. A pool that will be used for both children and adults for games and general recreation should have shallow areas at each end and a 5-foot-deep area in the middle. A pool used primarily for swimming laps should have a uniform depth of 4 or 5 feet from one end to the other.
Pools used for diving must be much deeper in areas of the pool where diving is allowed. Minimum water depths vary depending on the size of the pool and the type of diving equipment installed but generally range between 7 1/2 and 9 feet.
A pool's water capacity in gallons depends on its total area and its average depth. A 12-by-24-foot rectangular pool with an average depth of 5 feet will hold approximately 10,800 gallons of water. A 16-by-32-foot pool with the same depth will hold about 19,200 gallons, and a 20-by-40-foot pool will hold 30,000 gallons.
When homeowners use an in-ground pool, the majority of their time is spent on the patio or deck that surrounds the pool, so the deck needs to be big enough to accommodate all the activities it will host. A typical deck has an area of between 600 and 900 square feet.
The deck must be big enough that all furniture is at least 30 inches from the edge of the pool, and all walkways must be at least 3 feet wide.