# 20x40 inground pool: size, cost and what it looks like

Updated 2026-10-10.

A 20x40 inground pool is 800 square feet of water with 120 feet of edge, and holds about 26,900 gallons at a 4.5 foot average depth. It is 5 fence panels long, a pool for entertaining on a large lot. The pool alone runs $70,000 to $200,000 at national planning rates.

## A 20x40 is 800 square feet, more than half again the water of a 16x32

Twenty by forty is a large residential pool. At 5 fence panels long it belongs on a deep, wide yard. Against a 16x32 it adds 288 square feet of water and about 9,700 gallons.

The AI concept image above shows a large freeform pool with rounded ends, not a rectangle, on an estate lot with an outdoor kitchen behind. It is a mood, not a measured 20 by 40. At this size there is room for a wide entry shelf, a [spa](https://rendersplash.com/pool-features#spa) with a spillway and a run of wall fountains without losing swimming water, and the picture shows all three.

## A 20x40 suits a big lot and a big household, and needs a bigger budget to match

A 20x40 is among the sizes vinyl liner pools are commonly sold in, according to one California pool builder's size guide, so it is a standard product and not a one-off. For a crowd, ask how many will be in the water together rather than how many could fit; the [people table in the guide](https://rendersplash.com/pool-sizes/what-size-pool-do-i-need#how-many-people) shows the figures side by side.

Because cost follows water area and edge, a 20x40 costs far more than a 16x32 to build and to run. More water means more chemicals, more heating and a larger cover. The planning table prices the pool line for both sizes so the gap is visible.

One pool maker suggests keeping a pool to no more than about a quarter of the yard, which puts a 20x40 on a yard of about 3,200 square feet.

A pool this size also changes how the yard is used. With 120 feet of edge there is a lot of coping, deck border and fence to plan, and the equipment that circulates 26,900 gallons is larger than the kind a small pool needs. Ask the builder who services it, how long a full turnover takes, and what the cover will look like across forty feet of water. Those answers belong in the written quote, not in a phone call.

## Covers, finishes, spas and decks are what grow a 20x40 price

Finishes, covers, spas and decks are the lines that grow a large pool's price, and the table below shows the pool and each extra line at its published rate. Ask every builder to price the same lines in the same order, so two quotes for a 20x40 can be compared line by line instead of by the total. A pool this size also costs more to heat and clean each year, which the [running cost section](https://rendersplash.com/inground-pool-cost#running-cost) of the cost page covers.

## What a 20x40 inground pool costs, line by line

| Line | Planning range | How it is worked out |
|---|---|---|
| The pool | $72,000 to $200,000 | 800 sq ft of water at $90 to $250 a square foot (shell, excavation, plumbing, equipment, plaster). |
| Coping | $500 to $6,500 | 120 linear ft of water edge at $6 to $55 a foot, from plain concrete to travertine. |
| A 4 ft deck border all round | $1,500 to $44,000 | 544 sq ft at $3 to $80 a square foot installed, from pavers to composite decking. |
| Aluminum pool fence around that deck | $2,500 to $5,500 | 152 linear ft at $15 to $35 a foot installed. |
| All of the above, if your quote includes it | $75,000 to $260,000 | Rounded |

## Questions people ask

**How many gallons is a 20x40 pool?** About 26,900 gallons at a 4.5 foot average depth, or 23,900 to 29,900 gallons at 4 to 5 feet.

**How big a yard does a 20x40 pool need?** One pool maker suggests keeping a pool to no more than about a quarter of the yard, so a 20x40 suits a yard of about 3,200 square feet, plus room for a deck and a fence. Check your town's setback rules, which differ from place to place.

**How much does a 20x40 inground pool cost?** At national planning rates, the pool alone comes to $70,000 to $200,000, and the full set of lines on this page reaches $75,000 to $260,000. A pool this size costs more to run too; see the [yearly running cost](https://rendersplash.com/inground-pool-cost#running-cost).

## Sources and date checked

Links checked 2026-10-06. A planning range from published sources, not a quote.

- [The California Pool & Spa Atelier, a California pool builder, swimming pool size chart, 2026](https://thecpsa.org/blog/swimming-pool-size-chart/)
- [Pool Research, pool volume, undated](https://poolresearch.com/pool-volume-calculator/)
- [Latham Pool, how small is too small, 2024](https://www.lathampool.com/blog/research/how-small-of-a-pool-is-too-small/)
- [HomeAdvisor, in-ground pool cost, 2026](https://www.homeadvisor.com/cost/swimming-pools-hot-tubs-and-saunas/inground-pool)
- [Fixr, gunite and concrete pool, 2025](https://www.fixr.com/costs/inground-gunite-concrete-swimming-pool)
- [Pool Research, plunge pool cost, undated](https://poolresearch.com/plunge-pool-cost/)
- [Pool Research, pool coping cost, 2026](https://poolresearch.com/coping-cost/)
- [HomeAdvisor, travertine pavers, 2026](https://www.homeadvisor.com/cost/outdoor-living/travertine-pavers-install/)
- [HomeAdvisor, pool deck cost, 2026](https://www.homeadvisor.com/cost/swimming-pools-hot-tubs-and-saunas/pool-deck)
- [Fixr, pool fence, 2025](https://www.fixr.com/costs/swimming-pool-fence)

Every picture on these pages is an AI concept image, not a built pool, and its proportions are not measured. Where a size has no picture of its own we show the closest one and say so in the text. Cost ranges are planning numbers from published guides at national rates, not quotes.

Pricing the whole job? See [inground pool cost, line by line](https://rendersplash.com/inground-pool-cost#line-items).

Will a 20x40 fit your yard? Try it in the planner: https://rendersplash.com/pool-sizes?s=20x40#size-planner

See a 20x40 in your own yard with the free visualizer: https://rendersplash.com/pool-visualizer