How to Calculate Spa Volume in Gallons

Proper water treatment and spa maintenance are dependent on the size of your spa, so it’s important to know the capacity of your spa in terms of gallons. Use the following formulas based on the shape of your spa as a guide to approximate your spa’s volume. Click here for printable version.

AVERAGE DEPTH
Depth of the Deep End + Depth of the Shallow End Divided by 2.
Example:

RECTANGULAR or SQUARE SPAS
Length x Width x Average Depth x 7.5 = Total Gallons
Example:

CIRCULAR SPAS
Diameter x Diameter x Average Depth x 5.9 = Total Gallons
Example:

OVAL SPAS
Long Diameter x Short Diameter x Average Depth x 5.9 = Total Gallons
Example:



IRREGULAR SPAS
Estimate section dimensions equivalent to rectangular, oval or circular spa. Calculate per formulas above.

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