Cubic Feet to Gallons Converter

Why pool volume gets worked out in cubic feet first

A pool or spa is a physical shape, so the honest first step is a volume in cubic feet: length × width × depth for a rectangular pool, or the equivalent for a round or oval one. Converting that cubic-foot figure into gallons is what actually tells you how much water -- and therefore how many chemicals -- you're dealing with, since every dosing rule in the Chemicals section is written per gallon.

The exact factor is 1 cubic foot = 7.480519 gallons, which comes from the definition of a US gallon as exactly 231 cubic inches (a cubic foot is 1,728 cubic inches, and 1,728 ÷ 231 = 7.480519…). Our own Pool Volume Calculator uses this same factor internally when it reports both cubic feet and gallons for your pool.

In practice, most pool owners only need this converter when they already have a cubic-foot figure from a contractor's spec sheet, a pump or filter manual, or a manual measurement, and want to translate it into the gallons every chemical label and dosing calculator expects.

Example: a spa listed at 50 cubic feet holds about 374 gallons -- small enough that a single 1 lb bag of shock is usually more than enough for a full treatment, unlike a full-size pool.

Where these numbers come from

The formulas and default values in this calculator are based on:

• NIST Handbook 44 and SI unit conversion factors (1 US gallon = 231 cubic inches exactly
• 1 cubic foot = 1,728 cubic inches, giving 7.480519 gallons per cubic foot)

These are planning estimates. Test your actual water, follow product labels, and check your equipment manufacturer's guidance before you buy or dose chemicals.