Hexagon Pool Volume Calculator

How to Use This Hexagon Pool Volume Calculator

What Is Hexagon Pool Volume?

Hexagon pool volume is the total amount of water your hexagonal pool holds, measured in US gallons, litres, or cubic feet. Knowing this number is the starting point for every maintenance decision — from how much chlorine to add to how long a full refill takes.

A regular hexagon has 6 equal sides and a symmetrical shape that is neither circular nor rectangular. That means a rectangle or circle formula will not produce the correct water volume. The hexagon needs its own shape-specific area factor — √3 ÷ 2 — applied to the flat-to-flat width before multiplying by depth.

Typical Hexagon Pool Sizes and Water Capacity

Hexagon pools are almost always custom-built. Flat-to-flat widths range from about 10 ft (3.0 m) for a compact plunge or spa up to 24 ft (7.3 m) or more for a full-size swimming pool. A 16 ft hexagon pool at 5 ft average depth holds 8,292 gallons (31,390 litres), while a 20 ft hexagon pool at the same depth holds 12,957 gallons (49,046 litres) — a 56% increase in water for just 4 extra feet of width.

Two hexagon pools with the same outer footprint can hold different volumes if the internal water dimensions or depth differ. Surface tile, coping overhangs, and bench seats all reduce the internal water area. Always measure the internal water surface from flat side to side, not the outer deck edge or coping lip.

The flat-to-flat width and the side length of a regular hexagon are related but not the same measurement. The side length is shorter by a factor of 1 ÷ √3 (about 0.577 of the flat-to-flat width). Entering the side length where the calculator expects the flat-to-flat width will understate area and volume by more than two-thirds.

How to Calculate Hexagon Pool Volume

A regular hexagon has 6 equal sides, which means it is not a circle and not a rectangle — it needs its own area formula. The pool volume formula for a hexagon applies the shape factor √3 ÷ 2 (approximately 0.866) to the square of the flat-to-flat width. This factor accounts for the exact proportion of the bounding square that a regular hexagon fills.

The Hexagon Pool Volume Formula

Surface Area = (√3 ÷ 2) × D²
Volume = Surface Area × Average Depth
US Gallons = Volume (ft³) × 7.48052 | Litres = Volume (ft³) × 28.3168

D is the flat-to-flat width — the perpendicular distance between two parallel flat sides, measured at the waterline. Average Depth is (Shallow End + Deep End) ÷ 2. The shape factor √3 ÷ 2 ≈ 0.866 represents the exact fraction of the bounding square that a regular hexagon occupies.

This factor is not the same as the octagon pool factor (≈ 0.828) or the round pool factor (π ÷ 4 ≈ 0.785). At the same flat-to-flat width, a hexagon encloses more area than an octagon or a circle, so using the wrong shape formula always produces the wrong volume — and the wrong chemical doses.

Unit consistency matters: if you measure in feet, the result is cubic feet. Multiply by 7.48052 for US gallons or 28.3168 for litres. If you measure in metres, multiply cubic metres by 1,000 for litres or by 264.172 for US gallons.

Worked Example: Hexagon Pool Volume

A custom hexagon pool has a flat-to-flat width of 24 ft, a shallow end of 3.5 ft, and a deep end of 6.5 ft.

A 24 ft hexagon pool is a common size for custom residential builds with a full shallow-end-to-deep-end slope, and 18,658 gallons (70,626 litres) falls in the mid-to-upper range of typical pool volumes.

How to Measure a Hexagon Pool

Measuring Hexagon Pool Dimensions

Three different distances exist on a regular hexagon, and only one belongs in the calculator:

• DIAMETER (flat-to-flat) — the perpendicular distance from one flat side to the opposite flat side. This is what the calculator accepts.
• Side length (s) — one of the 6 equal edges. Related by s = D ÷ √3, or about 0.577 × D.
• Corner-to-corner diagonal — the longest straight line, from one vertex to the opposite vertex. Equal to D × 2 ÷ √3, or about 1.155 × D.

The corner-to-corner diagonal is about 15.5% larger than the flat-to-flat width. Entering the diagonal where the flat-to-flat width is expected overstates the area — and therefore the volume — by exactly one-third (33.3%). On a 20 ft hexagon pool, that error inflates the result from 12,957 gallons (49,046 litres) to roughly 17,276 gallons (65,395 litres).

Calculating Average Depth

If your hexagon pool has a sloped floor, measure the water depth at the shallowest point and the deepest point. The calculator uses: Average Depth = (Shallow End + Deep End) ÷ 2. For a flat-bottom pool, enter the same depth in both fields — the calculator confirms the floor is flat and the result is exact.

Hexagon Pool Volume by Size — Reference Table

Calculated using the hexagon pool formula with internal flat-to-flat width and average water depth. Do not use the corner-to-corner diagonal. 1 cu ft = 7.48052 US gal = 28.3168 L. Average depth = 5.0 ft based on 3.5 ft shallow and 6.5 ft deep water.

This range covers compact spa-size hexagons through full residential swimming pools. A 4 ft increase in flat-to-flat width adds roughly 2,500–5,000 gallons (9,500–19,000 litres), depending on where in the range you start. For more shapes and sizes, see the pool volume by size reference.

Hexagon Pool vs Octagon Pool — Volume Comparison

At the same flat-to-flat width and depth, a regular hexagon pool holds about 4.5% more water than a regular octagon pool. The reason is purely geometric: the hexagon shape factor is 0.866 while the octagon factor is 0.828. The hexagon fills a larger proportion of the bounding square than the octagon does.

For a 20 ft flat-to-flat pool at 5.0 ft average depth:

• Hexagon: 346.41 ft² surface area → 12,957 US Gal (49,046 Litres)
• Octagon: 331.37 ft² surface area → 12,394 US Gal (46,917 Litres)
• Difference: 563 US Gal (2,129 Litres)

The 563-gallon gap is not large in absolute terms, but it is enough to affect chlorine concentration by 0.2–0.4 ppm at a standard 2 ppm target. If you dose a hexagon pool using octagon measurements or vice versa, your chemical levels will be consistently off. Use the correct shape — the octagon pool volume calculator for 8-sided pools, and this page for 6-sided hexagons.

Hexagon Pool vs Round Pool — Volume Comparison

A hexagon and a round pool can look similar from across a yard, but they use different formulas and different measurement inputs. A round pool needs a single diameter (edge to edge through the centre). A hexagon pool needs the flat-to-flat width, which is measured between two parallel flat sides — not between corners.

At a 20 ft flat-to-flat width and 5.0 ft average depth, a hexagon pool holds 12,957 gallons (49,046 litres). A round pool with the same 20 ft diameter holds 11,750 gallons (44,480 litres). The hexagon holds about 10.3% more water because its straight edges extend beyond the inscribed circle at each flat side.

The polygon edges of a hexagon make mismeasurement more likely. A round pool has one simple dimension — any straight line through the centre works. A hexagon pool, on the other hand, has three distinct widths (flat-to-flat, side length, and corner-to-corner), and choosing the wrong one changes the result by up to one-third.

Why Hexagon Pool Volume Matters for Chemicals, Refill Planning, and Heating

Chemical dosing depends directly on true water volume. Chlorine, pH adjusters, and algaecide labels specify amounts per gallon or per litre. Over-dosing a hexagon pool because the volume was overstated can irritate skin and damage surfaces; under-dosing allows algae and bacteria to grow. Always follow the product label and your equipment specifications for your exact pool setup. For a detailed look at dosing by volume, see pool volume and chemical dosing.

Refill planning depends on gallons or litres. A standard garden hose delivers about 9 gallons (34 litres) per minute. Filling a 12,957-gallon (49,046-litre) hexagon pool from empty takes roughly 24 hours of continuous flow — useful to know before you start a drain-and-clean.

Heating costs scale with total water volume, not visible surface area alone. A hexagon pool and a round pool with the same footprint width hold different volumes, so the heating bill differs too. Equipment manuals typically need gallons or litres to size the heater correctly.

Circulation pump sizing also depends on total water volume. Most residential pools need the full volume to turn over at least once every 8–12 hours. Under-sizing a pump because the calculated volume was too low reduces filtration and shortens equipment life.

Common Mistakes When Estimating Hexagon Pool Volume

1. Using the corner-to-corner diagonal instead of the flat-to-flat width. The diagonal is about 1.155 times the flat-to-flat width. Squaring the larger number overstates the area by exactly one-third (33.3%), adding thousands of gallons to the result. Measure between two parallel flat sides.
2. Confusing the side length with the flat-to-flat width. The side length of a regular hexagon is about 0.577 × the flat-to-flat width. Entering the side length where the flat-to-flat width is expected understates the area by more than two-thirds. The calculator labels the field "DIAMETER (flat-to-flat).
3. Using a round or octagon formula for a hexagon pool. The round factor is π ÷ 4 ≈ 0.785 and the octagon factor is ≈ 0.828. Neither matches the hexagon factor of ≈ 0.866. Applying the round formula to a 20 ft hexagon pool underestimates volume by about 1,200 gallons (4,540 litres).
4. Measuring to the coping or outer deck edge instead of the internal water surface. Coping overhangs and decorative edges extend 2–4 inches beyond the waterline on each side. On a 20 ft hexagon pool, measuring the outer deck edge instead of the water surface overstates the flat-to-flat width and inflates volume by 300–600 gallons (1,135–2,271 litres).
5. Using a single depth measurement instead of averaging shallow and deep ends. A hexagon pool with a 3.5 ft shallow end and a 6.5 ft deep end has a 5.0 ft average depth. Using the deep end alone overstates volume by 30%; using the shallow end alone understates it by the same amount.
6. Mixing feet and inches incorrectly. A depth of 4 ft 6 in is 4.5 ft, not 4.6 ft. A 0.1 ft error on a 20 ft hexagon pool changes the result by about 260 gallons (984 litres). Convert inches to decimals by dividing by 12 (e.g., 6 in ÷ 12 = 0.5 ft).

Frequently Asked Questions