Pool Volume in Gallons Calculator
Pool volume is the water surface area times the average depth, converted to gallons. One cubic foot holds 7.48 US gallons, an exact conversion from the definitions of the gallon and the foot. For a rectangular pool the area is length times width; for a round pool it is pi times the radius squared. Use the average depth, halfway between the shallow and deep ends, not the deepest point. Knowing the volume is the starting point for chemical dosing and for sizing pumps, filters, and heaters. Enter your shape and dimensions below.
Pool volume formula
Rectangular area = length * width
Round area = pi * (diameter / 2)^2
Volume (cu ft) = area * average depth
Gallons = volume (cu ft) * 7.48
Liters = gallons * 3.785411784
One cubic foot equals 7.48 US gallons (1,728 cubic inches divided by 231 cubic inches per gallon). One US gallon is exactly 3.785411784 liters. Use the average depth for sloped-bottom pools.
Pool volume context
- One cubic foot of water is 7.48 US gallons, an exact unit conversion.
- Use the average depth, halfway between shallow and deep ends, not the deepest point.
- Round pools use pi times the radius squared for surface area.
- Volume is the basis for chemical dosing and for sizing pumps, filters, and heaters.
- The CDC notes that safe disinfection depends on knowing the water volume.
Pool volume: frequently asked questions
How do I calculate pool volume in gallons?
Find the water surface area, multiply by the average depth to get cubic feet, then multiply by 7.48 to convert to US gallons (one cubic foot is 7.48 US gallons). For a rectangle the area is length times width; for a round pool it is pi times the radius squared. Use the average depth, not the deepest point.
What is the average depth?
For a pool with a shallow and deep end, the average depth is roughly the shallow depth plus the deep depth, divided by two, if the bottom slopes evenly. Use that average, not the deep-end figure, or you will overstate the volume. For a constant-depth pool the average equals the actual depth.
Why convert cubic feet to gallons with 7.48?
One US gallon is defined as 231 cubic inches, and one cubic foot is 1,728 cubic inches, so a cubic foot holds 1,728 divided by 231, which is about 7.48 US gallons. This is an exact unit conversion, not an estimate, and is the standard factor used in US pool and water calculations.
Why do I need the pool volume?
Volume is the basis for dosing chemicals such as chlorine and for sizing pumps, filters, and heaters. Chemical labels give doses per a number of gallons, so an accurate volume keeps water balanced. The CDC notes that proper disinfection depends on knowing the water volume.
Does pool shape change the formula?
Only the area part changes. Rectangular pools use length times width; round pools use pi times radius squared; oval and kidney shapes are approximated from their bounding dimensions or split into simpler areas. Once you have the surface area, the depth and 7.48 conversion are the same for any shape.
Official sources
- U.S. Centers for Disease Control and Prevention: Healthy Swimming.
- U.S. National Institute of Standards and Technology: NIST Unit Conversion (volume units).
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.