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Volume & Capacity · A3

Oval Pool Volume Calculator

Instant volume for oval pools in gallons, liters & cubic feet — enter the long and short axes.

Measure the inputsMeasure the long axis and short axis at the waterline through the center of the pool.
Read the full resultAn oval holds about 21% less water than a rectangle of the same length and width — the rounded ends remove volume.
Check the boundaryFor oval above-ground pools with buttressed sides, measure the actual water shape, not the deck footprint.

Useful forVolume & CapacityPlanningComparisonVerification

Live calculation

Pool dimensions

✓ Checked May 2026

Enter the long axis (length), short axis (width), and depths.

Change a value. See the result.

Required fields are marked *. Engine validation and warnings remain active.

Enter the known values. Let the engine handle the calculation.

✓ Formula checked↻ Live result○ No account needed

Planning estimate only. Confirm product labels, equipment specifications, qualified-professional advice and local requirements before acting.

The result, explained

Use the Oval Pool Volume Calculator result with context.

Instant volume for oval pools in gallons, liters & cubic feet — enter the long and short axes.

01

The purpose

What does this calculator estimate?

Instant volume for oval pools in gallons, liters & cubic feet — enter the long and short axes.

02

The tool

What information does it use?

  • Length (long axis): The longest straight-line distance across the water.
  • Width (short axis): The widest distance perpendicular to the length.
  • Shallow end depth: enter a measured or verified value
  • Deep end depth: enter a measured or verified value
  • Hose / fill rate: Garden hose: 5–17 GPM depending on pressure & diameter.
  • Local water rate: Average US municipal water: $0.004–0.008 / gallon.
03

The method

How to use this calculator

  1. Length (long axis)The longest straight-line distance across the water.
  2. Width (short axis)The widest distance perpendicular to the length.
  3. Shallow end depthEnter the value you can verify.
  4. Deep end depthEnter the value you can verify.
  5. Hose / fill rateGarden hose: 5–17 GPM depending on pressure & diameter.
  6. Local water rateAverage US municipal water: $0.004–0.008 / gallon.
04

The relationship

The formula in plain English

Volume = π × (Length ÷ 2) × (Width ÷ 2) × Avg. Depth × 7.48

An oval is an ellipse: area = π × semi-major × semi-minor axis | ×7.48 converts ft³ → US gallons
05

Worked through

A worked example: 16 × 32 ft oval pool, 3 ft shallow / 6 ft deep

  1. Avg depth = (3 + 6) ÷ 2 = 4.5 ft
  2. Surface area = π × (32÷2) × (16÷2) = π × 16 × 8 = 402 ft²
  3. Volume = 402 × 4.5 × 7.48 = 13,536 gallons
All figures assume an average depth of 4.5 ft.
Pool size (L × W)Surface areaVolume (US gal)Volume (litres)Water weightFill time @ 9 GPM
10 × 20 ft157 ft²5,28720,01622.0 tons~10 hrs
12 × 24 ft226 ft²7,61428,82431.7 tons~14 hrs
15 × 30 ft354 ft²11,89645,03249.6 tons~22 hrs
16 × 32 ft402 ft²13,53651,23756.4 tons~25 hrs
18 × 36 ft509 ft²17,13164,84171.4 tons~32 hrs
20 × 40 ft628 ft²21,14980,05188.2 tons~39 hrs
06

Why it matters

How the result supports the next decision

Measure the long axis and short axis at the waterline through the center of the pool.

An oval holds about 21% less water than a rectangle of the same length and width — the rounded ends remove volume.

07

Good inputs

Improve the estimate before relying on it

  • Measure the long axis and short axis at the waterline through the center of the pool.
  • An oval holds about 21% less water than a rectangle of the same length and width — the rounded ends remove volume.
  • For oval above-ground pools with buttressed sides, measure the actual water shape, not the deck footprint.
  • If your pool is more of a 'stadium' shape (straight sides, semicircle ends), the ellipse formula slightly underestimates — add 2–3%.
  • Re-measure after a liner change; new liners can sit slightly differently and shift the effective dimensions.
08

The boundary

How to interpret the result

Measurements, equipment specifications, site conditions and local requirements can change the practical result.

The engine reports invalid inputs and safety warnings beside the result. Resolve those messages before using the estimate.

09

Before acting

What should override this estimate?

  • Measured site conditions and current test results
  • Product labels and manufacturer specifications
  • Qualified-professional advice and applicable local codes
10

Common questions

Frequently asked questions

What's the difference between an oval and a stadium-shaped pool?

A true oval (ellipse) curves continuously, while a stadium shape has two straight parallel sides capped by semicircles. The ellipse formula used here is accurate for true ovals. For stadium shapes, it underestimates volume slightly — add about 2–3% to the result.

Why do I enter two different measurements for an oval pool?

An oval has two axes: a long one (length) and a short one (width). Unlike a circle, these are different, so the formula needs both. It treats them as the semi-major and semi-minor axes of an ellipse to find the surface area.

How many gallons is a 15 × 30 ft oval pool?

A 15 × 30 ft oval pool at 4.5 ft average depth holds approximately 11,896 US gallons. The oval shape holds about a fifth less than a 15 × 30 rectangle because of the curved ends.

Can I use this for an oval above-ground pool?

Yes. Enter the long and short axes of the water surface and use the same value for shallow and deep depth, since most oval above-ground pools have a flat floor. The result gives you the volume for chemical dosing and fill planning.

How accurate is the ellipse formula for a real pool?

For a genuine oval, it's accurate within 1–2%. The main source of error is measuring the axes — take them at the waterline through the true center, and round to the nearest half-foot. Don't measure across the deck or coping.

How many gallons is a 12 × 24 ft oval pool?

A 12 × 24 ft oval pool at 4.5 ft average depth holds approximately 7,614 US gallons (28,820 litres).

How many gallons is an 18 × 36 ft oval pool?

An 18 × 36 ft oval pool at 4.5 ft average depth holds approximately 17,131 US gallons — a common large oval in-ground size.

Is an oval pool measured across the longest part?

Yes. The length is the longest straight line across the water; the width is the widest line perpendicular to it. Both are measured at the waterline through the center.

Primary sources

Use the result with current guidance.

These official references support safe planning context. Product labels, local requirements and qualified-professional advice take priority over a general calculator estimate.