Grecian Pool Volume Calculator

How to Use This Grecian Pool Volume Calculator

This Grecian pool volume calculator returns your pool's water volume in US gallons, litres, and cubic feet. Enter your pool's length, width, corner cut, and depth — the tool computes the result instantly.

Start by selecting your unit system — Imperial (feet) or Metric (metres) — using the toggle at the top of the calculator. Imperial mode shows gallons as the primary result. Metric mode shows litres first.

1. LENGTH (L) — the full end-to-end distance of the Grecian pool. Measure as if the corners were not cut — from one outer bounding edge to the other, not along a wall panel.
2. WIDTH (W) — the full side-to-side distance. Measure the widest span of the bounding rectangle, perpendicular to the length.
3. CORNER CUT (C) — the diagonal edge length of one clipped corner. Toggle to Measured mode and enter the tape-measured value for ±1–2% accuracy. In Estimate mode, the calculator uses 11.67% of the shorter dimension automatically.
4. SHALLOW END DEPTH (D₁) — the distance from the waterline to the pool floor at the shallowest point. Measure straight down, not along a sloped wall.
5. DEEP END DEPTH (D₂) — the distance from the waterline to the deepest point. For a flat-bottom Grecian pool, enter the same value as D₁.

Results appear instantly in the right-hand panel. The primary display shows gallons or litres depending on your unit selection, with secondary lines for the alternate unit and cubic volume. Use the result to dose chemicals, estimate fill time, or size a pool heater.

Manufacturer spec sheets list the outer shell dimensions — measure inner wall to inner wall at water level for an accurate volume input on a Grecian pool.

What Is Grecian Pool Volume?

Grecian pool volume is the total amount of water your Grecian pool holds when filled to the waterline, expressed in US gallons, litres, or cubic feet. This single number drives chemical dosing, pump sizing, heater selection, and refill planning.

A Grecian pool cannot use a plain length × width formula because its four clipped 45° corners reduce the water surface area below that of a true rectangle. The rectangle-minus-corners formula (L × W − C²) accounts for the missing corner triangles, producing a net surface area that matches the actual water boundary. Without that correction, the volume would be overstated by the area of the four clipped triangles multiplied by the average depth.

What Does Corner Cut Mean in a Grecian Pool?

Corner Cut (C) is the diagonal length of one angled edge at any corner of a Grecian pool. Each corner is a right-isosceles triangle cut from the bounding rectangle at a 45° angle. Because all four corners are identical on a standard Grecian pool, measuring one corner gives you the value for all four.

The area of one corner triangle is C² / 4. Four of them add up to C². That is why the formula subtracts C² from the rectangle area — not 4 × C or 2 × C. A 3 ft corner cut removes 9 sq ft of surface area total, while a 2 ft corner cut removes only 4 sq ft. The difference between those two values at 5 ft average depth is 187 gallons (708 litres) — enough to matter for chemical dosing.

Measure the corner cut by placing the tape where the straight wall panel ends and running it along the angled wall to the point where the next straight panel begins. That diagonal measurement — not the horizontal or vertical projection — is the correct C value for the formula.

How to Calculate Grecian Pool Volume

A Grecian pool is a rectangle with four identical 45° corner cuts. A standard rectangular pool volume calculator over-estimates the water area because it ignores the clipped corners. The Grecian formula subtracts the four corner triangles to produce the true surface area — a step that an oval pool volume calculator handles differently with π-based geometry.

The Grecian Pool Volume Formula

Volume (ft³) = (L × W − C²) × Average Depth
Average Depth = (Shallow End + Deep End) ÷ 2

Cubic feet → US gallons: × 7.48052

Cubic feet → Litres: × 28.3168

L = full outer length of the bounding rectangle. W = full outer width. C = the diagonal length of one corner cut edge. C² equals the combined area of all four right-isosceles corner triangles (each triangle has area C²/4, and 4 × C²/4 = C²). All dimensions must use the same unit — all feet or all metres — before multiplying.

The corner cut removes a small but measurable area. On a 20×40 ft Grecian pool with a 3 ft corner cut, C² = 9 sq ft — only 1.1% of the 800 sq ft bounding rectangle. The effect on volume grows with larger corner cuts.

Step-by-Step Worked Example

Pool: 20 × 40 ft Grecian pool, Corner Cut = 3 ft (measured), Shallow End = 3.5 ft, Deep End = 6.5 ft.

A 20×40 ft Grecian pool at this depth holds enough water to fill roughly 370 standard bathtubs. That volume figure is the starting point for every chemical dose, heater BTU calculation, and pump flow rate. For chemical dosing tables matched to your exact volume, see pool volume chemical dosing.

How to Measure a Grecian Pool

Measuring Length, Width, and Corner Cut

Length and Width describe the full bounding rectangle — the imaginary box that surrounds the Grecian pool before the corners are cut. Stretch the tape from one outer edge to the opposite outer edge, not from wall panel to wall panel. Measuring between the straight wall panels instead of the full bounding edges is the most common Grecian pool measurement mistake — it under-reports both dimensions and under-estimates volume by 8–15%.

Corner Cut (C) is the diagonal edge of one of the four clipped corners. Place one end of the tape where the straight wall meets the angled cut, then run it to the opposite end of that cut. All four corners on a standard Grecian pool are equal, so one measurement applies to all. Typical residential Grecian pools have a corner cut between 2 ft and 4 ft (0.6–1.2 m).

Calculating Average Depth

Average Depth = (Shallow End + Deep End) ÷ 2. For example: (3.5 + 6.5) ÷ 2 = 5.0 ft. Measure depth from the waterline straight down to the Grecian pool floor — not along a sloped wall or a hopper bottom.

Most Grecian pools have a gradual slope from the shallow end to a hopper or deep-end bowl. The two-point average approximates total water volume within ±3% for gradual slopes. For Grecian pools with a flat shelf that drops sharply into a deep section, measure at 3 evenly spaced points along the length and average all 3 for a tighter result.

Grecian Pool Volume by Size — Reference Table

The table below shows the volume of a Grecian pool at 8 standard sizes. All rows use 5.0 ft average depth (shallow 3.5 ft + deep 6.5 ft). Corner cut values are estimated at 11.67% of the shorter dimension — your measured corner cut may differ slightly.

Grecian Pool Volume Table

Calculated using (L × W − C²) × Average Depth, where C is estimated at 11.67% of the shorter side. 1 cu ft = 7.48052 US gal = 28.3168 L. Average depth = 5.0 ft (shallow 3.5 ft + deep 6.5 ft) ÷ 2. Measure your own Grecian pool for precision.

Residential Grecian pools typically range from 14×28 ft (14,562 gallons / 55,123 litres) up to 24×48 ft (42,794 gallons / 161,994 litres). The most popular size is 20×40 ft, holding 29,718 gallons (112,496 litres) at 5 ft average depth. For a complete breakdown across all pool shapes, see pool volume by size. Enter your exact dimensions in the calculator above for depths other than 5 ft.

Estimate vs Measured Corner Cut Mode

Estimate mode calculates the corner cut as 11.67% of the pool’s shorter dimension. For a 20×40 ft Grecian pool, the estimated C is 2.33 ft. No tape measure is needed — enter Length, Width, and Depth, and the calculator handles the rest. Results in Estimate mode fall within ±5–10% of actual volume, depending on how close the builder’s cut matches the 11.67% assumption.

Measured mode accepts the actual diagonal length of one corner edge. With a tape-measured C, results narrow to ±1–2% accuracy. Switch to Measured mode when you can physically reach a corner of the Grecian pool with a tape measure and need a tighter number for chemical dosing or heater sizing.

For a 20×40 ft Grecian pool, the difference between Estimate (C = 2.33 ft, 29,718 gal) and Measured (C = 3 ft, 29,585 gal) is only 133 gallons (0.4%). If you cannot measure the corner, Estimate mode gives a reliable starting point. Measure the corner when precision matters.

When to Use “I Know My Pool’s Surface Area”

Expand the advanced panel below the main calculator when you already have a verified total surface area from builder plans, a surveyed measurement, or a satellite image trace. Enter the surface area and average depth — the calculator multiplies them directly and bypasses the corner-cut geometry entirely.

This mode is especially useful when the Grecian pool has slightly unequal corners, worn edges, or a non-standard cut angle. In those cases, the (L × W − C²) formula assumes perfectly equal 45° corners and may over- or under-estimate the area by a few square feet. A builder-provided surface area eliminates that assumption.

Average depth is still required. Enter (Shallow End + Deep End) ÷ 2, or a single uniform depth if the pool floor is flat.

Grecian Pool vs Rectangular Pool Volume

A rectangular pool of the same bounding dimensions holds slightly more water because it has no clipped corners. A 20×40 ft rectangle at 5 ft average depth holds 29,922 gallons (113,267 litres). A 20×40 Grecian pool with an estimated corner cut of 2.33 ft holds 29,718 gallons (112,496 litres) — a difference of 204 gallons (0.7%).

The gap widens with larger corner cuts. A 4 ft measured corner cut on the same 20×40 pool drops the volume to 29,325 gallons (110,982 litres), making the difference 597 gallons (2.0%) versus the rectangle. For chemical dosing, that 2% gap translates to a measurable difference in chlorine and acid quantities over a full season.

A Grecian pool should never be treated as a plain rectangle in dosing or refill calculations. Always use the corner-cut formula or the measured surface area to avoid overstating the volume.

Why Accurate Grecian Pool Volume Matters

Chemical dosing depends on true water volume. Chlorine, pH adjusters, and algaecide labels specify amounts per gallon or per litre. Over-dosing a Grecian pool because the volume was overstated can irritate skin and damage surfaces; under-dosing allows algae and bacteria to grow. For dosing tables matched to your exact volume, see pool volume and chemical dosing.

Pump and circulation planning depends on total gallons or litres. Most residential Grecian pools need the full volume to turn over at least once every 8–12 hours. A pump rated for the wrong volume either runs too long or fails to circulate the water fully.

Heater sizing uses volume to estimate BTU requirements. A 30,000-gallon Grecian pool needs a larger heater than a 25,000-gallon pool to reach the same target temperature in the same number of hours. Using the bounding rectangle instead of the corner-cut formula overestimates the volume and may lead to purchasing an oversized heater.

Refill planning depends on accurate volume. A standard garden hose delivers about 9 gallons (34 litres) per minute. Filling a 29,585-gallon (111,993-litre) Grecian pool from empty takes roughly 55 hours of continuous flow. Use the pool volume calculator to run your exact dimensions before scheduling a drain-and-clean.

Common Mistakes When Measuring a Grecian Pool

1. Measuring wall panels instead of the full bounding rectangle. The straight wall panels of a Grecian pool are shorter than the full length and width because the diagonal corners eat into both dimensions. Measuring panel to panel under-reports the bounding rectangle and under-estimates the volume by 8–15%.
2. Guessing the corner cut instead of measuring it. Estimate mode is a useful fallback, but different builders use different corner sizes. A 2 ft corner cut and a 4 ft corner cut on the same 20×40 pool create a 597-gallon (2,260-litre) volume difference. Measure one corner with a tape for ±1–2% accuracy.
3. Measuring outside the coping instead of at the waterline. Coping and decorative edging extend 2–4 inches beyond the inner pool wall on each side. On a 20 ft width, that adds up to 8 inches of false width, inflating the area and the final volume by several hundred gallons.
4. Using only one depth instead of the shallow/deep average. A Grecian 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 margin.
5. Mixing feet and metres in the same calculation. Entering length in feet and width in metres produces a meaningless number. Use the Imperial/Metric toggle and enter all dimensions in the same unit system.
6. Assuming all Grecian pools have the same corner cut. Corner cuts vary by builder, pool size, and era. A 1990s Grecian pool may have a 2 ft corner cut; a custom-built 2020s pool may have a 4 ft cut. Always measure or verify against builder specs.

Grecian Pool Water Volume in Litres

This Grecian pool water volume calculator returns litres alongside gallons automatically. The conversion uses the precise factor 1 cu ft = 28.3168 litres.

For the 20×40 ft Grecian worked example above: 3,955 cu ft × 28.3168 = 111,993 litres. You can also convert from gallons directly: 29,585 gal × 3.78541 = 111,993 L. Both paths produce the same result because the conversion constants are mathematically equivalent.

If you need litres for an Australian, UK, or European context, switch the unit toggle to Metric and enter your Grecian pool dimensions in metres. The calculator multiplies m³ by 1,000 for litres and by 264.172 for US gallons. A 6 × 12 m Grecian pool at 1.5 m average depth holds approximately 107,424 litres (28,376 gallons). For a full guide to litre-based pool volume conversions, see pool volume formulas.

Frequently Asked Questions