D-Shaped Pool Volume Calculator

Select Imperial or Metric at the top of the input panel. Imperial shows results in US gallons and cubic feet; Metric shows litres and cubic metres.

Enter your D-shaped pool dimensions:

1. TOTAL LENGTH (L) — the overall distance from the flat wall to the furthest point of the curved end. Do not measure only the straight rectangular section — the calculator needs the full length including the semicircle. Pool builders typically quote this as the overall pool length.
2. WIDTH (W) — the full internal distance across the flat wall, measured from inner wall face to inner wall face. This equals the diameter of the semicircular end. Do not measure to the coping or deck edge.
3. SHALLOW END DEPTH (D₁) — the water depth at the shallowest point, measured from the waterline straight down to the pool floor. Do not use excavation depth from building plans if it differs from actual water level.
4. DEEP END DEPTH (D₂) — the water depth at the deepest point. For a flat-bottom D-shaped pool, enter the same value as the Shallow End. The calculator averages both depths automatically.

Results display in US gallons, litres, and cubic feet simultaneously. Use the volume for chemical dosing, pump sizing, heating estimates, and refill planning.

Pool builders typically quote the overall length from the flat wall to the tip of the curved end, but the straight rectangular section is shorter — on a 32 × 16 ft D-shaped pool, only 24 ft of that total length is straight because the curved end accounts for 8 ft.

D-shaped pool volume is the amount of water your pool holds when filled to the normal waterline. It is expressed in US gallons, litres (L), or cubic feet (ft³). The number depends on four inside measurements: overall length, width at the flat wall, shallow-end depth, and deep-end depth.

The shape matters because a D-shaped pool has one flat straight wall and one semicircular curved end. The curved end holds less water than a full rectangular corner would, so a D-shaped pool always holds less than a rectangle with the same overall length and width. Using a standard rectangular volume table for a D-shaped pool overestimates the true water volume.

Residential D-shaped pools commonly range from 24 × 12 ft at the smaller end to 40 × 20 ft or larger. Popular mid-range sizes include 28 × 14, 32 × 16, and 36 × 18 ft. At 5.0 ft average depth, a 32 × 16 ft D-shaped pool holds 18,123 gallons (68,602 L), while a 40 × 20 ft pool holds 28,317 gallons (107,190 L).

Two D-shaped pools with the same overall length can hold different water volumes if the width or depth profile differs. A wider pool increases both the rectangular section and the semicircular end area. Depth changes shift volume just as strongly — a 32 × 16 ft pool at 4.0 ft average depth holds about 14,498 gallons (54,882 L), compared with 18,123 gallons (68,602 L) at 5.0 ft.

The curved end reduces total volume compared with a full rectangle of the same overall footprint. A 32 × 16 ft D-shaped pool holds about 5.4% less water than a 32 × 16 rectangle, because the semicircular end replaces a rectangular corner area.

Marketing dimensions from pool builders often describe the overall frame or coping size, not the internal water dimensions. Measure from the inside face of the pool wall at the waterline for the most accurate volume result.

A D-shaped pool is a composite shape — one rectangular section joined to one semicircular end. No single simple-shape formula handles both parts correctly. A rectangular pool volume calculator covers only the straight portion, and a round calculator covers only circles. The D-shaped formula combines both components into one calculation.

The rectangular section calculation uses the straight portion of the pool: (L − W/2) × W. Here L is the overall length from the flat wall to the tip of the curved end, and W is the width at the flat wall. Subtracting W/2 from L isolates the straight rectangular section because the semicircular end extends W/2 beyond the dividing line.

The semicircle calculation uses (π/8) × W², which equals ½ × π × r² where the radius r = W/2. This gives the area of the curved end. The formula uses π/8 because substituting r = W/2 into the semicircle area formula simplifies to π × W² / 8.

The calculator expects the overall length — the full distance from the flat wall to the furthest point of the curved end — not the straight rectangular section alone. A 32 × 16 ft D-shaped pool has an overall length of 32 ft, a width of 16 ft, and a derived rectangular section length of 24 ft (32 − 8). The pool volume formula guide covers the conversion constants used for all pool shapes.

Keep all measurements in the same unit system. Mixing feet for length and metres for depth produces an incorrect result.

A 32 × 16 ft D-shaped in-ground pool with a 3.5 ft shallow end and a 6.5 ft deep end:

A 32 × 16 ft pool is a common residential D-shaped size. Using the curved-end composite formula instead of a full rectangular estimate prevents overestimating water volume by about 1,027 gallons (3,889 L) — the amount a full rectangle would falsely add.

Overall length is the straight-line distance from the inside face of the flat wall to the furthest point of the curved end. Do not follow the curved wall perimeter — that gives a longer reading and produces an incorrect total length.

Width is measured at the flat wall, from inner wall face to inner wall face. This is the widest point of the pool and also equals the diameter of the semicircular end. The semicircle radius is half the width: r = W ÷ 2.

The straight rectangular section length is derived from these two measurements. Rectangle length = Overall length − (Width ÷ 2). For a 32 × 16 ft D-shaped pool: rectangle length = 32 − 8 = 24 ft. The calculator performs this subtraction automatically when you enter the overall length and width.

D-shaped pools with a sloped floor need an average of the shallow-end and deep-end water depths. Average Depth = (Shallow Depth + Deep Depth) ÷ 2. A pool with a 3.5 ft shallow end and a 6.5 ft deep end has an average depth of 5.0 ft.

If the D-shaped pool has a flat bottom at a single uniform depth, enter the same value in both depth fields. The calculator treats equal depths as a flat-bottom pool and uses that single value directly.

Calculated using the D-shaped composite formula: rectangular section area plus semicircular end area, multiplied by average depth. Straight rectangular section length = overall length − (width ÷ 2). Average depth is 5.0 ft based on 3.5 ft shallow and 6.5 ft deep water.

The smallest D-shaped pool in this table holds 10,194 gallons (38,589 L) and the largest holds 34,263 gallons (129,700 L) — a 3.4× range. Depth changes shift volume just as strongly as footprint size. For comparisons across pool shapes, see the pool volume by size reference. For any D-shaped size not listed, use the calculator above with your exact measurements or browse our pool volume calculators for other shapes.

For identical overall dimensions of 32 × 16 ft at 5.0 ft average depth, a D-shaped pool holds 18,123 US gallons (68,602 L) while a full rectangular pool holds 19,150 US gallons (72,491 L). The D-shaped pool holds about 1,027 gallons (3,889 L) less — roughly 5.4% less water.

The difference comes from the curved end. A full rectangle fills the entire length × width footprint with water. A D-shaped pool replaces one rectangular end with a semicircle, which has a smaller area than the rectangular corner it replaces. The wider the pool relative to its length, the larger the percentage difference becomes.

This matters for chemical dosing, refill planning, and heating estimates. Dosing chlorine for 19,150 gallons when the pool actually holds 18,123 gallons leads to overtreatment by about 5.7%. Heating cost estimates based on a rectangular volume slightly overstate the energy needed.

Chemical dosing depends on true water volume. Chlorine, pH adjusters, algaecides, and salt are all dosed per gallon or per litre. A 32 × 16 ft D-shaped pool holds 18,123 gallons (68,602 L) — dosing for 19,150 gallons (the full rectangular estimate) would overtreate the water. Always follow the product label and your equipment specifications for your exact pool setup. The chemical dosing guide explains volume-based calculations in detail.

Pump circulation planning relies on total water volume. Most residential pools need one full turnover every 6 to 8 hours. A D-shaped pool holding 18,123 gallons needs a pump delivering at least 38 gallons per minute (GPM) to complete a turnover in 8 hours. Using a rectangular volume estimate would oversize the pump specification slightly.

Heating costs scale with the total gallons or litres being warmed. A 40 × 20 ft D-shaped pool at 28,317 gallons (107,190 L) costs roughly 56% more to heat per degree than a 32 × 16 ft pool at 18,123 gallons, assuming similar insulation and equipment efficiency.

Refill and partial-drain planning is easier when the curved-end deduction is accounted for correctly. Draining 25% of a 32 × 16 ft D-shaped pool means replacing about 4,531 gallons (17,151 L). At a typical garden hose flow of 10 gallons per minute, that refill takes roughly 7.5 hours.

1. Using a full rectangular formula instead of the D-shaped composite formula. Calculating 32 × 16 × 5.0 ft with a simple rectangle formula gives 19,150 gallons (72,491 L). The correct D-shaped volume is 18,123 gallons (68,602 L) — the rectangular estimate overstates the actual water by 1,027 gallons (3,889 L).

2. Entering only the straight rectangular section as the overall length. The calculator expects the full distance from the flat wall to the tip of the curved end. If a 32 × 16 ft D-shaped pool is measured as 24 ft (the straight section only), the result drops to about 13,335 gallons (50,479 L) — a 26% underestimate.

3. Measuring to the coping or deck edge instead of the inner wall face. On a 32 × 16 ft D-shaped pool, coping typically extends 3 to 6 inches beyond the pool wall on each side. Using the outer measurement adds about 840 gallons (3,180 L) to the estimate at 5.0 ft average depth.

4. Using a single deep-end depth instead of the average. A 32 × 16 ft D-shaped pool with a 3.5 ft shallow end and a 6.5 ft deep end has an average depth of 5.0 ft. Entering only the 6.5 ft deep-end depth overstates the volume by about 5,436 gallons (20,578 L).

5. Measuring along the curved wall perimeter instead of the straight-line overall length. The semicircular wall is longer than the straight-line distance across it. Taping a measure along the curved wall gives a reading that exceeds the true overall length, inflating the calculated volume.

6. Mixing feet and inches without converting. If the pool is 32 feet long and 6 feet 6 inches deep, the depth entry should be 6.5 ft, not 66. Entering 66 into a field expecting feet would inflate the volume by more than 10 times. Confirm all dimensions are in the same unit before entering them.