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Proper water treatment and hot tub maintenance are dependent on the size of your hot tub, so it is important to know the capacity of your hot tub in terms of gallons. Use the following formulas based on the shape of your hot tub as a guide to approximate your hot tub’s volume. Click here for a printable version.
The most accurate way to determine the volume of a hot tub, without fancy equipment, is by fill time. First, using a stopwatch or wristwatch time how long it takes to fill your hot tub. Convert minutes and seconds to total seconds, and write it down. Then, using the same hose and pressure, time how many seconds it takes to fill a one gallon bucket.
Now divide the number of seconds it took to fill your hot tub, by the number of seconds it took to fill the one gallon bucket, and you will have the approximate water volume! For example: You filled your hot tub in 30 minutes (1800 seconds) and filled the one gallon bucket in 6 seconds. 1800 divided by 6 = 300 gallons.
Using a five gallon bucket will result in an even smaller margin of error. Using the above example with a five gallon bucket: You filled your hot tub in 1800 seconds, and filled the five gallon bucket in 30 seconds. 1800 divided by 30 = 60 five gallon buckets, or 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 hot tub.
Our formulas make it easy because you use the outside dimensions of your portable hot tub cabinet.
* Results are estimated volume only. Consult with manufacturer.
These types have fewer interior water-displacing features, so this formula takes that into account.
* Results are estimated volume only. Consult with manufacturer.