Pool Gallon Calculator estimates water volume for any pool shape, converts cubic units to gallons, and previews formulas with examples.
Rectangular volume = L × W × D × 7.48052; with L=30, W=15, D=5.5 → gallons ≈ …
A Pool Gallon Calculator determines how much water your pool holds so you can size pumps, heaters, and chemicals correctly. It accepts essential dimensions—length, width or diameter, and average depth—then applies geometry to compute volume and converts that volume to U.S. gallons (and optionally liters). Because chemical dosing, winterization, and equipment selection depend on accurate capacity, a transparent formula preview helps you verify measurements and understand assumptions (e.g., using average depth for sloped bottoms and measuring to the current waterline, not to the coping).
The calculator uses the universal relationship Volume = Surface Area × Average Depth. For common shapes it computes surface area directly; for irregular or freeform pools it recommends splitting the surface into simpler sections (rectangles, circles, ovals), adding their areas, and multiplying by average depth. Conversions use U.S. gallons (1 ft³ = 7.48052 gal). If you prefer metric, it can show liters (1 ft³ = 28.3168 L; 1 gal ≈ 3.78541 L). To reduce error, it explains how to average depth and how to approximate special shapes like kidney pools with two semicircles and a center rectangle.
Rectangular/square: \[ V_{\text{ft}^3}=L\cdot W\cdot \bar d. \]
Circular: \[ V_{\text{ft}^3}=\pi r^2\bar d=\pi\left(\tfrac{D}{2}\right)^2\bar d. \]
Oval (ellipse): \[ V_{\text{ft}^3}=\pi \left(\tfrac{L}{2}\right)\left(\tfrac{W}{2}\right)\bar d. \]
Kidney (approximate area): \[ A\approx \left(L-\tfrac{W_1+W_2}{2}\right)\tfrac{W_1+W_2}{2}+\frac{\pi}{8}(W_1^2+W_2^2),\quad V_{\text{ft}^3}=A\,\bar d. \]
Units and conversions: \[ \text{Gallons}=V_{\text{ft}^3}\times 7.48052,\qquad \text{Liters}=V_{\text{ft}^3}\times 28.3168. \]
Fill time (minutes) at flow \(F\) GPM: \[ t_{\text{min}}=\frac{\text{Gallons}}{F}. \]
\(L=30\,\text{ft},\ W=15\,\text{ft},\ d_\text{sh}=3.5\,\text{ft},\ d_\text{dp}=5.5\,\text{ft}\Rightarrow \bar d=4.5\,\text{ft}\). \(V=30\cdot15\cdot4.5=2025\,\text{ft}^3\Rightarrow \text{Gallons}\approx2025\times7.48052\approx15{,}148\).
\(D=24\,\text{ft},\ \bar d=4.0\,\text{ft}\). \(V=\pi(12)^2\cdot4\approx1809.6\,\text{ft}^3\Rightarrow \text{Gallons}\approx13{,}536\).
\(L=32\,\text{ft},\ W=16\,\text{ft},\ \bar d=5\,\text{ft}\). \(V=\pi(16)(8)\cdot5\approx2010.6\,\text{ft}^3\Rightarrow \text{Gallons}\approx15{,}040\).
\(L=30\,\text{ft},\ W_1=18\,\text{ft},\ W_2=12\,\text{ft},\ \bar d=4.5\,\text{ft}\). \(A\approx408.78\,\text{ft}^2,\ V\approx1839.5\,\text{ft}^3\Rightarrow \text{Gallons}\approx13{,}761\).
Measure to the current waterline; capacity changes with water level.
\(\bar d=(d_\text{shallow}+d_\text{deep})/2\). For multiple shelves, use a weighted average by surface area.
Liters ≈ gallons × 3.78541. U.S. gallons are used here (not Imperial).
Typically within a few percent if widths and length are measured carefully; complex shapes benefit from sectional breakdown.
Yes—compute volume in m³ and convert: 1 m³ = 1000 L ≈ 264.172 gal.
Time (minutes) = gallons ÷ GPM. Example: 10,000 gal at 8 GPM ≈ 1250 minutes ≈ 20.8 hours.
About 13.5k gallons (see Example 2).
Different depth assumptions, rounding, or shape factors. Use the same inputs and method for consistency.
Most dosing is ppm-based. Grams needed ≈ Δppm × (gallons × 3.78541) ÷ 1000.
Yes—treat them as shallow sections (add their volume) for more accuracy.
Capacity reduces when water is below the usual line; recalc if level changes significantly.
Yes—knowing gallons helps estimate BTUs needed to raise temperature by a target ΔT.