Find Out How Many Gallons Your Hot Tub Holds

Knowing the amount of water that your hot tub holds is important when determining how many chemicals are needed when dosing it for shock treatment or cleaning. Figuring it out can be a little tricky, especially if you have misplaced your manual, where that information is almost always printed for your convenience. 

On average a hot tub holds anywhere from 300 gallons to 675 gallons, depending on the size. You can figure out the amount by calculating the width, depth, length or diameter if circular, or using the fill-up method and timing how long it takes to fill the hot tub, which can take 1 ½ to 2 hours. 

With the average amount of gallons a hot tub holds being 300 gallons for a 2 to 3-person hot tub and 675 gallons for a 6 to 8-person hot tub, you are looking at quite a range if you are simply guessing. So let’s look at how you can figure out the exact amount of gallons your hot tub holds in order to get a better idea of how many chemicals your hot tub needs.

How Many Gallons Are in the Average Hot Tub?

Close-up of water jets inside hot tub

The amount of water that your hot tub will hold depends on its size. A smaller hot tub will hold less water, and a larger one will hold more. 

Generally speaking, a 2 to 3-person hot tub will hold roughly 300 gallons of water, a 4 to 5-person hot tub will have 275 to 375 gallons, and finally, a 6 to 8-person hot tub will hold 675 gallons or more. 

How to Calculate the Number of Gallons in Your Hot Tub

Knowing the precise amount of water that your hot tub holds can help when dosing it with chemicals that help maintain its water quality. There are a few ways to do this, the easiest being to look in the hot tub manual. 

Usually, that information is listed in the manual, and if the manual was misplaced or thrown out, then a search on Google with the make and model of your hot tub could easily provide those answers for you. 

However, if you can’t find that information online or in the manual, then you can always do a little math to come up with the exact amount of gallons your hot tub holds. For this method, you’ll need to have a tape measure handy.

  1. With a square or rectangular hot tub, you will need to use that tape measure and figure out the length, width, and depth of the hot tub.

  2. Multiply the width by the depth.

  3. Divide that number by 1,728. 1,728 is the number that is used to convert cubic inches to cubic feet.

  4. For round hot tubs you have to measure the width across the central point of the hot tub as well as the depth.

  5. Once the diameter is calculated, multiply that number by the depth.

  6. Divide that number by 1,728.

  7. If your hot tub comes with seats, multiply your result by 2.4. If your hot tub does not have seats, multiply it by 4.8 instead.

  8. Once multiplied for seats or not, you will have your answer on how many gallons of water fit inside of your hot tub.

If math isn’t your strong suit, there is another method to figure out the number of gallons of water that fit in your hot tub. The timed fill method uses a hose and a timer.

  1. Turn on your hose and run it into your hot tub.

  2. Using a timer, keep track of how long it takes to reach its full capacity.

  3. Once full, calculate how many seconds it took to fill.

  4. Get an empty gallon-sized jug.

  5. Using your hose to fill that jug, time how long it takes to become full. The number of seconds you get is your flow rate per gallon.

  6. Divide the time it took to fill the jug by the time it took to fill your hot tub. This number will then give you the approximate gallons that your hot tub holds.

How Long Does It Take to Fill a Hot Tub?

Determining how long it takes to fill up your hot tub depends on a number of things. 

The first thing to consider is the water pressure at your property. If you have a weak water pressure, then it will take a lot longer than if it were strong. The second aspect to think about is the size of the hot tub. The larger it is, the longer it will take to fill. 

The last thing to consider is the hose size you will be using if you are filling up a portable hot tub. With a narrow nozzle or hose, less water will get through at a time, which will increase the wait time to fill your hot tub. 

Generally speaking, it takes roughly one and a half to two hours to fill a decent-sized hot tub of 300 to 400 gallons, while a hot tub designed for six to eight people will take approximately two to three hours to fill. 

How to Determine What Hot Tub Size You’ll Need

Hot tub

The size of a hot tub that you should get depends on several different factors that are unique to your situation.

The first thing to consider is the location of the hot tub. If you plan to put your hot tub on a deck, you need to calculate how much weight that deck can hold. Generally, decks aren’t designed to hold the heavy weight of a filled hot tub with people inside of it and will most likely need to be reinforced if your hot tub is on the larger or heavier side.

If you plan to place your hot tub on a patio or concrete slab, then you have a lot more wiggle room on the size that can be accommodated. At that point, you are looking more at the width and length of the hot tub that can then fit comfortably in the space available. 

The next thing to consider is what you will use the hot tub for or who will be using it. If you like to host a lot of gatherings with lots of people, then you might be best suited for a larger hot tub that can hold more people. 

However, if it is only for immediate household members or even just yourself, then a smaller hot tub will be able to accommodate you comfortably. 

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