Pool Volume Calculator

Knowing your pool capacity is the foundation for pool maintenance. All chemical treatments (chlorine dosage, algaecides, pH balancers) and pump sizing calculations require an accurate gallon capacity to avoid dangerous under-dosing or over-dosing.

A standard approximation is to find the average width (add narrowest width to widest width and divide by 2) and use the oval formula, multiplying by a shape modifier of 0.85 to account for the inward curves.

Always calculate to the target water line (typically midway up the skimmer opening, which is about 4 to 6 inches below the top coping edge) to reflect the actual water weight and capacity.

One US gallon of pool water weighs approximately 8.34 pounds. A 20,000-gallon pool holds roughly 166,800 pounds (83.4 tons) of water, which is important for structural load calculations.

Multiply the US gallon volume by 3.78541 to get liters. For example, 15,000 gallons × 3.78541 = 56,781 liters. If you have Imperial gallons (UK), multiply by 4.54609 instead.

No, the physical water volume is identical. However, saltwater pools require you to calculate salt dosage based on the same gallon capacity, typically needing 2,500 to 3,500 ppm of sodium chloride.

Use a weighted tape measure or pool depth marker. Most pools have depth markers at the shallow and deep ends. If not, measure from the water surface to the pool floor at both ends with a marked pole.

Pool volume refers to the total cubic measurement of the water space. Pool capacity typically refers to the same measurement expressed in gallons or liters. They are essentially the same value in different units.

The calculator is highly accurate for standard geometric pool shapes. Freeform and kidney-shaped estimates use a shape modifier and may vary by 5 to 15 percent from the actual volume depending on the severity of curves.

Yes. Enter the interior dimensions of the hot tub. Most residential hot tubs hold 300 to 500 gallons. For irregularly shaped spas, measure the approximate rectangular envelope and reduce by 20 to 30 percent.

A standard 16×32 inground pool with an average depth of 5.5 feet holds approximately 21,064 gallons. At 4 feet average depth it holds about 15,328 gallons, and at 6 feet average depth it holds about 22,990 gallons.

A 15×30 pool with an average depth of 5 feet holds approximately 16,830 gallons. With a 4-foot average depth, it holds about 13,464 gallons.

A 15-foot round above-ground pool that is 48 inches (4 feet) tall holds approximately 5,310 gallons. A 18-foot round pool of the same depth holds about 7,646 gallons.

Most residential pools have a shallow end of 3 to 4 feet and a deep end of 6 to 8 feet, giving an average depth of 4.5 to 6 feet. The national average for inground pools is approximately 5.5 feet.

A pool with a uniform slope from shallow to deep end is well approximated by the average depth formula. Pools with a flat shallow area and sudden deep-end drop require a two-zone calculation for best accuracy.

Steps and built-in benches displace water, reducing actual volume by 2 to 8 percent. For precise calculations, subtract the approximate volume of step and bench structures from the geometric total.

For a rectangular pool, multiply length × width × 0.0833 (one inch in feet) × 7.48 to get gallons per inch. For example, a 16×32 pool holds approximately 319 gallons per inch of water depth.

Pool heaters are rated in BTUs per hour, and the required BTU output depends directly on water volume. Larger volumes require more energy to raise temperature by one degree, so accurate volume ensures proper heater selection.

The standard dosage is 1 to 3 ppm of free chlorine. For shocking, use 1 pound of granular chlorine per 10,000 gallons. Accurate volume measurement prevents both under-chlorination and chemical waste.

You only need to recalculate if you alter the pool structure (add steps, change depth markers, or reshape). Water level fluctuations from evaporation do not change the pool's physical volume capacity.

The Pool Volume Calculator uses verified mathematical formulas processed entirely in your browser. Calculator inputs and results are never sent to external servers. We do use Google Analytics and AdSense for standard website operation — see our Privacy Policy for details.

Yes. All calculations happen locally in your browser. We never store, transmit, or log any input data you enter into the calculator.

Double-check that all inputs are valid numbers within reasonable ranges. If you believe there is an error, please contact us with your input values and we will investigate.