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Choose your pool shape below to open the correct volume calculator — 20 shapes covered, results in gallons and litres.
Why Pool Shape Determines Your Calculator
Pool shape is the single biggest variable that changes which formula you need. A 16×32 ft rectangular pool at 5 ft depth holds about 19,200 gallons, but the same 16×32 ft footprint as an oval holds just 15,080 gallons — a 21% difference from one shape constant alone. The oval formula applies the 0.7854 ellipse factor (π ÷ 4), which removes the area outside the curve that a rectangle would include. Chemical dosing, pump sizing, heater BTU calculations, and salt-cell output all depend on an accurate volume, so choosing the correct shape calculator is the first step to getting your numbers right.
Select your pool shape from the 20 options below to open the matching calculator with the right formula already applied.
Round / Circular Pool
A pool with a uniform circular shape — the most common above-ground pool form.
Oval Pool
An elongated ellipse — common for above-ground and some inground pools.
Rectangular Pool
Four right-angle corners — the most common inground pool shape.
Kidney Pool
One concave side and one convex side — a classic freeform inground shape.
L-Shaped / Lazy L Pool
Two connected rectangles forming an L — common for pool-and-spa combination designs.
Grecian Pool
A rectangle with all four corners cut at a diagonal — a symmetrical classical shape.
Lagoon Pool
A wide, irregular organic shape resembling a natural lagoon — broader than kidney.
Roman Pool
A rectangle with one or both short ends replaced by a semicircular arch.
Octagon Pool
Eight equal sides — common for above-ground decorative pools and spas.
Freeform Pool
A completely custom organic shape with no standard geometry.
Plunge Pool
A small, deep rectangular pool designed for immersion — typically 6–10 ft wide.
Hot Tub / Spa
A small heated soaking pool — circular or rectangular, typically 5–8 ft across.
Triangular Pool
A three-sided pool — found as corner features, spa sections, or standalone designs.
Square Pool
Four equal sides — a modern minimalist inground pool design.
Lap Pool
Long and narrow — typically 7–10 ft wide and 40–75 ft long, for continuous swimming.
Infinity Pool
A pool where the water appears to vanish at one edge — includes a balance tank.
D-Shaped Pool
One flat straight end and one curved semicircular end — popular in UK gardens.
Hexagon Pool
Six equal sides — a decorative above-ground or inground feature pool.
Figure-8 Pool
Two circular or oval pools connected at the centre — a dual-area design.
T-Shaped Pool
Three connected rectangles forming a T — offers separate swim and lounge areas.
Not Sure What Shape Your Pool Is?
Answer one question to narrow down your pool shape:
Question 1: Does your pool have straight sides only and right-angle corners?
→ Rectangular, Square, L-Shaped, T-Shaped, or Lap pool.
Question 2: Does your pool have curved sides throughout?
→ Round, Oval, Kidney, Lagoon, or Freeform pool.
Question 3: Does your pool combine straight and curved sections?
→ Grecian, Roman, D-Shaped, Figure-8, Infinity, or Octagon.
When none of these match, use the freeform pool volume calculator — divide the pool into recognisable sections, calculate each section separately, and add the volumes together.
Pool Volume Formula by Shape — Quick Reference
| Shape | Formula | Constant Explained |
|---|---|---|
| Round / Circular Pool | π × r² × Average Depth | π ≈ 3.14159 — ratio of circumference to diameter |
| Oval Pool | π × (L/2) × (W/2) × Average Depth | Equivalent to L × W × 0.7854; 0.7854 = π/4 |
| Rectangular Pool | L × W × Average Depth | No shape constant — full rectangle area |
| Kidney Pool | ٠.٤٥ × (A+B) × L × Average Depth | 0.45 — industry empirical factor for kidney concavity |
| L-Shaped / Lazy L Pool | (L₁×W₁ + L₂×W₂) × Average Depth | No constant — two-rectangle addition method |
| Grecian Pool | L × W × ٠.٨٥ × Average Depth | 0.85 — clipped-corner reduction factor |
| Lagoon Pool | L × W × ٠.٧٨٥ × Average Depth | 0.785 ≈ π/4 — freeform ellipse approximation |
| Roman Pool | (Rectangular + Semi-circle surface area) × Average Depth | Semicircle area = π × r² / 2 |
| Octagon Pool | ٢(١+√٢) × s² × Average Depth | 2(1+√2) ≈ 4.828 — regular octagon area factor |
| Freeform Pool | L × W × ٠.٧٨٥ × Average Depth | π/4 bounding-box approximation (±15–25%) |
| Plunge Pool | L × W × POOL DEPTH | No constant — rectangular with deeper depth |
| Hot Tub / Spa | π × r² × POOL DEPTH (نصيحة Round / Circular Pool) | Shape-dependent; usually round or square |
| Triangular Pool | (Base × Height / ٢) × Average Depth | ÷ 2 — half the bounding rectangle area |
| Square Pool | Side² × Average Depth | No shape constant — full square area |
| Lap Pool | L × W × Average Depth | No constant — narrow rectangle formula |
| Infinity Pool | Your pool Volume + Balance tank Volume | Balance tank typically adds 5–10% extra volume |
| D-Shaped Pool | (Rectangular + Semi-circle surface area) × Average Depth | Semicircle area = π × r² / 2 |
| Hexagon Pool | (٣√٣/٢) × s² × Average Depth | (3√3/2) ≈ 2.598 — regular hexagon area factor |
| Figure-8 Pool | π × r₁² + π × r₂² × Average Depth | Two circles summed; overlap zone subtracted |
| T-Shaped Pool | (L₁×W₁ + L₂×W₂) × Average Depth | No constant — two-rectangle addition method |
Full formula explanations with worked examples for every shape are available at the pool volume formula reference.
Frequently Asked Questions
Does pool shape really affect the volume calculation?
Yes. Pool shape determines which formula applies. A 16×32 ft rectangular pool at 5 ft depth holds approximately 19,200 gallons (72,680 L). The same 16×32 ft footprint as an oval holds approximately 15,080 gallons (57,090 L) — 21% less — because the oval formula uses the 0.7854 constant to remove the area outside the ellipse. Using the wrong formula produces an inaccurate volume that affects every chemical dosing calculation.
Which calculator should I use for an irregular pool?
Use the freeform pool volume calculator or divide the pool into recognisable sections. A kidney shape uses the 0.45 × (A+B) × length formula, where A is the widest measurement and B is the narrowest. For a pool combining a rectangle and a semicircle — such as a Roman end pool — calculate each section with its own formula and add the two volumes together. The freeform method works for any irregular shape.
Are above-ground and inground pool formulas different?
No. Pool type does not change the formula — pool shape does. An 18 ft round above-ground pool and an 18 ft round inground pool both use π × 9² × depth × 7.48. The practical difference is depth input: above-ground pools have flat bottoms so enter actual wall depth; inground pools typically have variable depth so enter the average of shallow end and deep end measurements.
What is the most common pool shape?
Rectangular is the most common inground pool shape across the United States. Round is the most common above-ground pool shape — standard sizes range from 10 ft to 33 ft in diameter, holding 2,400 to 52,000 gallons (9,085 to 196,845 L) at 4 ft depth. Kidney is the most recognisable freeform inground design. Use the shape selector above to find the correct calculator for your pool.
Can I calculate pool volume without knowing the exact shape?
Yes, using the freeform sectional method. Divide the pool into the closest recognisable shapes — rectangles, circles, or triangles — that approximate the pool's outline. Calculate the volume of each section separately using the correct formula for that shape, then add all section volumes together. The result will be accurate to within 2–5% for most irregular pools if measurements are taken carefully.