Pool Pump Size Calculator: Find The Correct Size Pump You Need

Pool Pump Calculator

Many factors go behind determining the right pool pump size, as it is the pump that will push all that pool water through the filter plant. It becomes imperative to decide on the right size pump, and by undertaking a few calculations, you will surely get it right.

How To Figure Out The Pool Pump Size:

The below-mentioned criterion must be taken into consideration while finding the correct pool pump to suit your requirements:

1. Pool Volume Calculation

The first step to find the correct pool pump size is to figure out the gallons of water that the swimming pool holds. The calculation is simple and is based on the pool size. The volume can be calculated when you know the dimensions and shape of your pool. The reason to do so is that the pool pump should turn over these gallons of water in about 8 hours.

Follow this simple formula depending on the shape of your pool:-

  • For a rectangular pool: length * width * average depth

  • For a circular pool: 3.14 * radius squared * average depth

Pool Volume Calculation

2. Minimum Flow Rate

After finding out the approximate gallons of water in your pool, the next step is to determine the pump’s minimum flow rate. It is done through the gallons per minute (GPM) calculation.

This calculation is based on the pool size and the turnover rate in a day. Generally, the standard is around two turnovers per day, whether it is a chlorine pool or a saltwater pool. The choices are to run the pump the whole day, that is, 24 hours or twice a day in a 6, 8, or 10-hour cycle.

The science and thought behind this is balancing the electricity bill due to appropriate pump horsepower and perfect water chemistry. Using a lower horsepower pump for a longer time results in balanced water chemistry, but it may hike up your electricity expenses.

You may also opt for variable speed pool pumps where the speed can be adjusted because of the use of magnet motors, resulting in perfect pool chemistry and energy efficiency.

Mini And Max Flow Rate

3. Maximum Flow Rate

It is the next thing to be figured out. It is based on the plumbing system and all the fancy equipment being used in the pool. Let us first talk about the filters:


Various types of pool filters are used in the pool. The most common ones are sand, cartridge, and DE filters. They are all different and have a different maximum flow rate, which depends on the surface area. We have mentioned below the flow rates for common filter types:

Sand Filter:

Sand filters generally occupy 19 – 22 Max GPM per square foot of surface area.

  • 1.8 square feet surface area would require 40 GPM capacity

  • 2.3 square feet surface area would require 50 GPM capacity

  • 3.1 square feet surface area would require 60 GPM capacity

  • 4.9 square feet surface area would require 100 GPM capacity

Cartridge Filters

These filters are much bigger and less accurate. They generally have a 0.3 – 0.35 GPM per square feet of surface area.

  • 100 square feet surface area will need a 30 – 38 GPM capacity

  • 200 square feet surface area will need a 55 – 75 GPM capacity

  • 300 square feet surface area will need 80 – 112 GPM capacity

  • 400 square feet surface area will need 100 – 150 GPM capacity.

DE Filters

De filters are a little expensive. You may plan for approximately 1.75 GPM per square foot of surface area using these filters.

  • 24 square feet surface area requires a 36 – 48 GPM capacity

  • 36 square feet surface area requires 54 – 72 GPM capacity

  • 48 square feet surface area requires 72 – 96 GPM capacity

  • 60 square feet of surface area will need 90 – 120 GPM capacity

The most common problem faces with the brand is the deterioration of the quality over the period of time like peeling issues and the bad warranty. Some Buyers also review that they have to pay for warranty support. The brand does not provide warranty over many parts of the tuba and most of the times avoid taking the replacements.

Although having a good reputation in the market, buyers aren’t very happy with the product they receive in return.

4. Plumbing

After sorting out which filter to use, it is time to determine the maximum flow rates for plumbing. The pipes’ pressure needs to be appropriate, and it must not be more than what they can handle.

The maximum flow rate depends on the pipe size, which the company clearly labels. Generally, a 1.5-inch pipe carries a 43 GPM capacity, a 2-inch pipe has 73 GPM capacities, and a 2.5-inch pipe has a maximum of 120 GPM of power.

The entire setup may have different pipes that have been used. The pipe leading to the spa will be different from the one leading to the pool. You must always go for the lowest of the maximum flow rate to avoid any setup damage.


5. The Flow Rate Range

After calculating the maximum and minimum flow rate for your pool, you need to put them together and get the flow rate range. To make it simpler, let us take an example:

Let’s say if you have a 15,000 gallon of the pool area with two turnovers per day, and the minimum flow rate is 20.8 GPM.

If you use a 2.3 square feet sand filter with 50 GPM maximum capacity and a 1.5-inch plumbing pipe with 43 GPM capacity, going with the principle of using the lower of the two values, your Max flow rate comes out to be 43 GPM.

So the flow rate range is 20.8 – 43 GPM.

The Flow Rate Range

6. Total Dynamic Head (TDH)

It is an important specification that tells about the total amount of resistance in the pool’s hydraulic system. Many things like the filter, pipes, heater, pump, etc., all affect the water flow in the system setup. Usually, the in-ground pools have approx. 50 TDH and above ground pools have 30 TDH.

Total Dynamic Head

Final Specifications:

All these factors play a significant role in determining your ideal pool pump. All the pump models mention horsepower estimates based on the flow rate and total dynamic head. Keeping in mind our specification list and recommendations for the best single and variable speed pump, you will surely be able to select the best one.

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