how many gallons in a hot tub

How Many Gallons in a Hot Tub? (Easy Formula)

If you are concerned about the water usage in a hot tub, most probably you may have already wondered how many gallons are in a hot tub.

Typically water usage depends on several factors including the size of the tub and the number of people. If your hot tub is for 2-3 persons, it may typically hold around 300 gallons. When the hot tub is for 4-5 persons, there should be 275-375 gallons of water. However, if you talk about a larger 6-8 person tub, it can hold up to 675 gallons of water.

If you want to dive further into this topic, continue reading as I am going to explain how to calculate the number of gallons in a hot tub. So, without further ado, let’s begin.

How to Calculate How Many Gallons in a Hot Tub

There are several reasons you may want to know the capacity of your hot tub. If you know the capacity, you will get an estimate of the estimated heating and cleaning cost, final weight, etc.

Although you can find a hot tub calculator, still you can do the calculation on your own. If you want to calculate the gallon capacity of a hot tub, you should follow this simple formula.

Firstly, you need to multiply the length, width, and depth of the hot tub by inches. Then, you must divide the outcome by 1728. Then, determine whether your hot tub comes with a seat or not. If it has seat, multiply the outcome by 2.4. But, when you have a hot tub that lacks seats, you should divide the result by 4.8.

The above calculation is compatible with all standard square or rectangle-shaped hot tubs. However, if your hot tub does not have a standard shape, the calculations will be different.

Typically, you can calculate the approximate capacity of a hot tub by two different methods which are as follows-

  1. Timed fill method
  2. Dimension calculation method

Below I will discuss in detail these two methods.

Calculating in Timed Fill Method:

The timed fill method is quite straightforward. But, you will need to have a bit of patience when you follow this method. Typically, the following steps are included in this method to calculate the gallon capacity of your hot tub.

Step 1- Fill up the Tab:

Turn on your hose and start to fill your hot tub with the hose water.

Step 2- Record the Filling Time:

Don’t forget to set a timer. Wait patiently until the hot tub is filled up completely with water. No wonder, it will take some time. But, you need to have patience here. When the tub is full, you must stop the timer.

Step 3- Convert the time to Seconds:

Now, it’s the calculation time. Our goal is to convert the recorded time to seconds. Firstly, multiply the number of hours by 60 to convert it into minutes. Then you need to add any additional minutes to the result. After that convert the total minutes by 60 so that you can get the result in seconds.

Step 4- Record the Converted Time:

Then you need to record this time in seconds for future calculation.

Step 5- Fill your One Gallon Jug With Water:

At this point, you need to take a 1-gallon jug and fill that with the hose water. Don’t forget to record the total filling time by using your timer.

Step 6- Convert the Recorded Time to Seconds:

Now, you need to convert the recorded time to seconds. Simply multiply the minutes by 60 and add additional seconds to the result. If you do so, you will get the time in seconds.

Step 7- Final Calculation:

All you have to do is a simple division. Just divide the total time needed to fill the entire tub by the time needed to fill a one-gallon jug. The result is the approximate capacity of your hot tub in gallons.

Calculating in Dimension Calculation Method:

In this method, you have to follow these simple steps to get the desired result.

Step 1- Take the Measurement:

If your tub is in a square or rectangular shape, you have to measure the width, length, and depth of it by using a decent tape measure. Don’t forget to take the measurements in inches.

On the other hand, if you have a round-shaped hot tub, you must take the measurements differently. In that case, you need to measure the diameter of the tub. To do that, you must center the tape measure straight across the middle of the unit.

Then, you need to take the depth measurement. Of course, record these measurements in inches here as well.

Step 2- The Multiplication:

To find volume in a square tab, multiply the length by width by depth. When it comes to the round tub, you need to multiply the diameter by the diameter of the depth. In both of the cases, you will get the result in cubic inches.

Step 3- Convert the Result into Cubic Feet:

At this point, you need to take the result from step 2 and divide it by 1728. It will give you a result in cubic feet.

Step 4- Final Calculation:

Check whether your hot tub has seats. If yes, then multiply the result from step 3 by 2.4. In this case, it is the final result. However, if the tub has no seat, you should multiply the result from step 3 by 4.8. It will give you the result.

That’s how you can calculate the number of gallons your hot tub holds.


Knowing how many gallons are in a hot tub will offer you a lot of benefits. There are a couple of methods by which you can calculate its gallon capacity. Whether you want to know how many gallons are in 6 person’s hot tub or an 8×8 hot tub, the procedures are pretty much the same.

If you follow the timed fill method, you need to complete the steps patiently. On the other hand, if you follow the dimension calculation method, follow the right procedures for the right shape of the tub.

I hope this article was helpful and now you will be able to calculate the number of gallons in a tub without any hassle.


Hi, I'm Shimul, the founder of Pooltub Life. I'm excited about sharing the latest outdoor living trends with you. My goal is to provide you with up-to-date information that will help make your POOL & HOT TUB stylish and enjoyable. Read About Me More । Follow on Facebook

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