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What Size Pool Pump Do I Need? Pool Pump Flow Rate Calculator

Working out which pool pump you need can be a mathematical challenge, but we’re here to make it as easy as possible. After all, pool pumps are one of the most important features of your pool. Without one your pool’s water wouldn’t be pumped or filtered efficiently.

What Size Pool Pump Do I Need?
What Size Pool Pump Do I Need?

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Where Do I Start?

Fitting the right pump depends on a number of factors, and you need to take everything into consideration, not just the size of your pool.

For example, it could be as easy as telling you to grab a 40GPM pump for a small pool and an 80GPM pump for a large pool. However, you may want to be a little more precise, seeing as the correct pool pump could not only save you cash on energy bills, but it could also be better for the environment.

Firstly, think about your pool pump in relation to the pool filter. Their GPM (gallons per minute) ratings are directly relatable and should always be considered. First of all, you always want to ensure that your pool filter’s GPM is higher than the GPM of your pump. This is because you want as little strain as possible on the pool pump, and a higher pool filter GPM will ensure this.

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Pool Pump Size

Another thing to think about is how much HP (horsepower) your pool pump will have. Naturally, the higher the HP rating, the more powerful the pump.

Even though this is the case, mistaking HP as being the most important factor would be remiss. You don’t just need the most powerful pump out there. That’s why it’s so important to take GPM into consideration.

Related Post: 3 Different Kind of Pool Pumps

Working Out the Correct Pump Size

It’s time to get a little mathematical.

Firstly, you need to work out how many gallons of water your pool holds. Let’s say for this example that your pool is 12ft x 24ft and holds 10,800 gallons of water. You can calculate the volume of your pool here.

Our second step is to discover how many gallons of water need to be pumped per hour, per day. The average pool needs to pump water for 8 or 10 hours per day. Let’s round it down to 8 hours for this example.

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To do this sum, simply take your total amount of gallons (10,800), and divide that by the amount of hours (8). You’ll end up with a sum that looks like this: 10,800 ÷ 8 = 1,350.

Now keep your answer close, because we aren’t quite done. This number simply tells you the amount of gallons that are moved throughout an 8-hour period. We still need to work out how many gallons are pumped per minute, as this is how they’re labelled.

Simply take your previous answer (1,350), and divide it by 60 (the amount of minutes in an hour). You’ll have a sum that looks like this: 1,350 ÷60 = 22.5GPM.

Pool Pump Flow Rate Calculator

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Minimum Flow Rate Calculator

Now you have a great way to find the answer to what size pump is best for your pool!

Our Recommended Pool Pumps


Best of the Best
Also Great
Less HP
Hayward W3SP1580X15 Power Flo Pool Pump, 1.5...
Pentair SuperFlo® VS Variable Speed Pool...
Polaris PB4-60 Booster Pump with 60-Hertz...
Hayward W3SP1580X15
Pentair 342001
Zodiac PB4-60
• 1.5 HP Pool Pump
• 115V
• Heavy-duty motor
• Extra-large debris
• Drain plug
• 20.5 x 6.5 x 8.5 in
• 24 pounds
• 1.5 HP Pool Pump
• 115-230V
• Digital control keypad
• Three programmable speeds
• Real-time, 24-hour clock
• 28 x 15.5 x 12.5 in
• 52 pounds
• 3/4 HP Pool Pump
• 115/230V
• Ergonomic drain plug
• Larger volute seal o-ring
• Quick and easy installation
• 17 x 9.5 x 14.5 in
• 31 pounds
The Hayward W3SP1580X15 is a high performance pool pump, featuring a heavy-duty motor, which provides dependable performance and quiet operation. An extra-large debris basket keeps pool maintenance to a minimum, letting you enjoy your pool more.
The Pentair 342001 Variable Speed Pump brings remarkable energy cost savings of variable speed technology to everyday pools that require up to a 1.5-HP pump. They dramatically reduce energy costs by moving water more efficiently at lower speeds.
Delivering the best combination of high-performance power and durability — this Zodiac Polaris PB4-60 Booster Pump is specifically designed to operate together with the Polaris pressure-side pool cleaners. Its compact, rugged design allows for maximum performance.
Best of the Best
Hayward W3SP1580X15 Power Flo Pool Pump, 1.5...
Hayward W3SP1580X15
• 1.5 HP Pool Pump
• 115V
• Heavy-duty motor
• Extra-large debris
• Drain plug
• 20.5 x 6.5 x 8.5 in
• 24 pounds
The Hayward W3SP1580X15 is a high performance pool pump, featuring a heavy-duty motor, which provides dependable performance and quiet operation. An extra-large debris basket keeps pool maintenance to a minimum, letting you enjoy your pool more.
Also Great
Pentair SuperFlo® VS Variable Speed Pool...
Pentair 342001
• 1.5 HP Pool Pump
• 115-230V
• Digital control keypad
• Three programmable speeds
• Real-time, 24-hour clock
• 28 x 15.5 x 12.5 in
• 52 pounds
The Pentair 342001 Variable Speed Pump brings remarkable energy cost savings of variable speed technology to everyday pools that require up to a 1.5-HP pump. They dramatically reduce energy costs by moving water more efficiently at lower speeds.
Less HP
Polaris PB4-60 Booster Pump with 60-Hertz...
Zodiac PB4-60
• 3/4 HP Pool Pump
• 115/230V
• Ergonomic drain plug
• Larger volute seal o-ring
• Quick and easy installation
• 17 x 9.5 x 14.5 in
• 31 pounds
Delivering the best combination of high-performance power and durability — this Zodiac Polaris PB4-60 Booster Pump is specifically designed to operate together with the Polaris pressure-side pool cleaners. Its compact, rugged design allows for maximum performance.


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Last Update: 2023-02-03 | Affiliate links/Images from Amazon Product Advertising API

About the author

Hi I’m Alex, founder of HouseholdMe.com and I’d like to say thank you for dropping by. Like most of you, the first thing I look at before buying something online is reviews or buying guides. By reading what other people say will help me gauge whether or not a product is good or not.  I am trying to help people find answers, solve problems, and get inspired.

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