Above-Ground Pool Size & Gallons Calculator

How to use the above-ground pool calculator

1. Measure the space: the flat, level ground you can give the pool, edge to edge.
2. Pick a shape and a wall height: round, oval or rectangle; 48″, 52″, 54″ or any.
3. You get the largest pool Intex and Doughboy sell that fits with 4 feet clear all round, how many gallons it holds, what the water weighs and presses on the ground, and every other size that fits, drawn from above to scale.

Want a hot tub beside it instead? The hot tub size calculator fits a tub to your spot and your deck.

The rules, and where they come from

The sizes sold. Intex’s US site and pump manuals list its frame pools: rounds from 12′ × 30″ to 26′ × 52″, ovals, and rectangles up to 16′ × 32′ × 52″. Doughboy’s site lists rounds from 8′ to 32′ and ovals from 12′ × 18′ to 21′ × 41′, in 48″, 52″ and 54″ walls.

The gallons. Intex prints its own: “Water Capacity (Calculated at 90% for Frame Pool and 80% for Easy Set Pool)”. Doughboy prints none, so its pools here are the shape’s own volume filled to 90% of the wall. A round is π × radius², and an oval has straight sides and round ends. Intex’s round pools come out 5–10% below that sum for the same size, because a pool’s inside is a little smaller than its name.

The space. Intex’s owner’s manual: “The pool requires at least 4 feet (1.22 m) of space all around pool from objects that a child could climb on to gain access to the pool.” The ground “must be absolutely flat and level”, “compacted and firm”, and never “a deck, balcony or platform”.

The outlets. The same manual: “a minimum distance of 6 ft (1.83 meters) from any receptacle”, and every 125-volt 15- and 20-amp receptacle within 20 ft on a GFCI.

The weight. A cubic foot holds 7.48 gallons (the US gallon is 231 cubic inches). Water weighs about 8.34 lb a gallon, so 48″ of it presses about 250 lb on every square foot of ground.

Intex’s gallons, size by size

From Intex’s sand filter pump manual 342PO (July 2025) and its product pages, at 90% full. Its filter pump manual 107 gives the 10′ × 20′ × 52″ rectangle as 5,611 gallons. 5,835 is that box filled to 90%.

Doughboy’s sizes and their gallons

Gallons are the shape filled to 90% of the wall; a dash means Doughboy does not list that wall for that size.

Worked examples

An 18′ round × 48″ pool: 6,423 gallons: a 26′ × 26′ patch of lawn less 4′ all round leaves 18′. Intex sells it as a Metal Frame, Ultra XTR or Prism Frame.

An 18′ round × 52″ pool: 6,981 gallons: the same space with a taller wall holds about 560 gallons more.

A 16′ × 32′ oval × 52″ pool: 13,334 gallons: a long, narrow 28′ × 40′ side yard takes an oval that a round of the same width could not fill.

A 10′ × 20′ rectangle × 52″ pool: 5,835 gallons: a 20′ × 30′ space fits Intex’s Ultra XTR rectangle with 4′ to spare each side.

A 12′ round × 48″ pool: 3,046 gallons: a 20′ × 20′ space leaves 12′ for the pool once 4′ is kept clear all round.

Common mistakes

• Measuring the pool, not the space. An 18′ pool needs a 26′ × 26′ spot with 4′ clear all round.
• Building up a low spot. The ground must be flat, level and firm; Intex says never sand, mud or soft soil.
• Putting it on a deck. Intex warns a deck “may collapse under the weight of the filled pool”: an 18′ × 48″ pool’s water alone weighs over 53,000 lb.
• Buying chemicals for the wall height. Dose by the gallons in the pool, filled to its line, not to the top of the wall.

More on backyard pools at Dreamy Home Style

• Creative above-ground pool ideas
• Above-ground pool landscaping
• DIY landscaping for an above-ground pool
• Semi-inground pool ideas
• Pool deck ideas

Laying out the whole yard? Draw it to scale in the free 2D floor planner.