How many gallons is in a 4 person hot tub?

A 4 person hot tub will typically hold between 200 and 400 gallons of water. The exact capacity depends on the dimensions and design of the particular hot tub model. In this article, we will discuss the factors that determine hot tub capacity and provide estimates for common 4 person hot tub sizes.

Typical Dimensions of 4 Person Hot Tubs

Most 4 person hot tubs are in the range of 5 to 7 feet long and 5 to 6 feet wide. The most common dimensions are:

  • 5 feet x 7 feet
  • 6 feet x 6 feet
  • 6 feet x 7 feet

Some compact 4 person hot tubs may be as small as 4 ft x 6 ft, while larger models can be up to 7 ft x 8 ft. The height of 4 person tubs is usually between 28 and 38 inches.

Estimating Gallon Capacity

The total gallon capacity of a hot tub is determined primarily by its length, width, and depth. Here are some common formulas used to estimate hot tub water capacity:

  • Length x Width x Average Depth x 7.5 = Gallons
  • (Length x Width x Average Depth) / 231 = Gallons

The number 7.5 represents the number of gallons in a cubic foot of water. The number 231 is the number of cubic inches in a gallon.


Here are some examples of how to estimate the gallons for common 4 person hot tub dimensions:

Dimensions Calculation Gallon Estimate
5 ft x 7 ft x 3 ft deep (5 x 7 x 3) / 231 = 226 gallons 226 gallons
6 ft x 6 ft x 4 ft deep (6 x 6 x 4) / 231 = 311 gallons 311 gallons
7 ft x 7 ft x 3.5 ft deep (7 x 7 x 3.5) / 231 = 422 gallons 422 gallons

As you can see, a typical 4 person hot tub holds between 200 and 400 gallons. Smaller tubs are on the lower end of this range, while larger ones can hold up to 400+ gallons.

Factors That Affect Hot Tub Capacity

In addition to basic length, width, and depth, there are a few other factors that can impact the overall water capacity of a 4 person hot tub:

  • Seating Capacity – More seats generally means more space taken up, resulting in less water capacity for a given set of dimensions.
  • Seat Shape/Design – The contours and shapes of the seats also impact how much space is available for water.
  • Water Features – Built-in waterfalls, fountains, etc. can displace water volume.
  • Steps/Benches – Models with steps and benches inside the tub itself take up some interior space.

When estimating hot tub capacity, you may need to make small adjustments to the calculations above depending on these other design factors. Tubs optimized for lounging tend to have more flourishes and displace more water than basic soaking tubs.

Common Capacities of Popular 4 Person Hot Tubs

To give you a better idea of real-world capacities, here are the published gallon specifications for some popular 4 person hot tub models:

Hot Tub Model Gallons
Coleman Saluspa 254 gallons
Lifesmart Rock Solid Simplicity 200 gallons
Home and Garden Sports Spa 170 gallons
Intex PureSpa Plus 295 gallons
Cal Spas Geneva 410 gallons

As you can see, most 4 person hot tub models fall into the 200 to 400 gallon range. The smallest budget tubs come in around 170 gallons, while larger premium spas can hold 400+ gallons.

Do Hot Tubs Need To Be Completely Filled?

It’s important to note that you do not need to completely fill a hot tub to the brim to use it. Most hot tubs are designed to operate safely and properly when filled 2/3 to 4/5 of full capacity.

Filling to the manufacturer’s recommended “minimum fill level” ensures there is adequate water for circulation and keeps the pump and heater properly submerged. This level is typically a few inches below the seats and jets.

So a 250 gallon hot tub may only need to be filled with 150 to 200 gallons to operate normally. Always follow your owner’s manual for proper fill levels.

How Much Does it Cost to Fill a 4 Person Hot Tub?

The cost to fill a 4 person hot tub depends on your local water rates and how many gallons it holds. Let’s look at some sample fill up costs for a 300 gallon tub:

  • At $5 per 1000 gallons, 300 gallons would cost $1.50 to fill
  • At $10 per 1000 gallons, 300 gallons would cost $3 to fill
  • At $15 per 1000 gallons, 300 gallons would cost $4.50 to fill

So for most areas, you can expect to pay $3 to $5 to completely fill a 300 gallon 4 person hot tub from empty. This assumes you are filling from your home’s garden hose spigot.

Ways to Save on Fill Up Costs

Here are a few tips to minimize the costs of filling your 4 person spa:

  • Only fill to the minimum level needed
  • Use a submersible pump and fill from a swimming pool
  • Fill up slowly over days/weeks with routed greywater

Ongoing Water Maintenance

In addition to initial fill up, hot tubs need occasional draining and refilling over time to keep the water clean and well-balanced. Here are some general guidelines:

  • Drain and refill your hot tub every 3-6 months
  • Replace at least 30% of the water monthly
  • Add fresh water weekly to replace what is lost from splashing/evaporation

The more frequently the hot tub is used, the more often you may need to change the water. Be sure to test chlorine, pH and other water chemistry regularly and follow your hot tub manufacturer’s draining guidelines.

Heating and Operation Costs

In addition to filling costs, hot tubs also require electricity to run pumps, heaters, and other components. Here are some estimates of operating costs:

  • Heating costs can range from $20 to $50+ per month depending on use
  • Pump operation may cost $5 to $20 per month
  • Other variable costs (lights, jets, etc) depend on frequency of use

So in total, you can expect to pay around $30 to $75 per month to operate a 4 person hot tub in most climates.

Ways to Save on Hot Tub Operation

You can reduce your operating expenses by:

  • Using an insulating cover whenever the hot tub is not in use
  • Setting the temperature lower when not expecting use
  • Running jets/lights only when the tub is occupied
  • Choosing a highly energy-efficient hot tub model

With smart use, you can minimize the recurring costs of enjoying your 4 person spa.


A 4 person hot tub will typically hold 200 to 400 gallons of water, depending on its exact dimensions. Smaller hot tubs may hold only 170 gallons, while larger models can hold 400+ gallons. You can estimate the capacity using length x width x average depth calculations.

When shopping for a new hot tub, remember that you do not have to completely fill it. Operation with 2/3 to 4/5 capacity is common. Heating and maintenance costs will add around $30 to $100 per month on average.

With some good planning and care, a 4 person hot tub can provide an affordable way to add luxury and relaxation to your backyard. Just be sure to account for all the costs before making your purchase.

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