"It's helpful to know your spa's water capacity to determine chemical dosages.  Textbook formulas for calculating volumes of geometric shapes do not work well for spas which have internal features such as seats and contours which displace water.  We've developed two methods to give you fairly accurate estimated hot tub water volumes."

Now divide the number of seconds it took to fill your spa, by the number of seconds it took to fill the gallon container, and you will have the approximate water volume!  For example:  You filled your spa in 30 minutes (1800 seconds) and filled the one gallon container in 6 seconds.  1800 divided by 6 = 300 gallons.

The dimensional method is not as accurate as the fill-time method, but is a quicker way to determine the approximate volume of any spa.

Use our handy pocket calculator
with the formulas below.

Portable Acrylic-Fiberglass Spas:

Our formulas make it easy because you use the outside dimensions of your portable spa cabinet. Take all measurements in inches:

• For Square or Rectangular portable acrylic spas:

• For Round or Multisided portable acrylic spas:

Results are estimated volume only.  Consult with manufacturer.

In-Ground Spas, Soft Spas, & Wooden Hot Tubs:

These types have fewer interior water-displacing features, so this formula takes that into account.  Take all measurements in inches:

• For Square or Rectangular types:

• For Round, Irregular, or Multisided types:

Results are estimated volume only.  Consult with manufacturer.