luxury rectangle pool at sunset

Whether you’re dreaming about having a brand-new, pristine pool installed in your backyard or you already have your oasis in place, being able to measure the size of your pool is basic knowledge every pool owner needs to know. The size of your pool dictates the size and type of many different support systems vital to maintaining a sparkling, well-functioning pool, and how much it will cost to get a pool cleaning service.

In this post, we’ll cover several aspects of pool measurements so you’ll always have the perfect set of dimensions to make sure your pool’s equipment and accessories are the right size for the job.  

Measuring Pool Size 101

Knowing your swimming pool’s size is actually two different measurements. One is the physical dimensions of the pool while the other is how many gallons of water the pool can hold. 

With these measurements in hand, you’ll be able to get the right size pool pump, heater, filter, and other accessories like a cover. Without accurate measurements, you can be left getting something either too big or too small to do the job right.

How to Measure Pool Size by Area

You’ll need to take measurements of the length and width of your pool in order to find its area. If your pool is a standard shape like a rectangle, this is straightforward. As an example, an olympic-size swimming pool has a standard size with a length of 50 meters and a width of 25 meters. Multiplying the length times the width, or 50m x 25m, yields a total surface area of 1,250 square meters. 

A great many pools, however, have steps, curves, or other irregular shapes that actually extend past the main body of the pool. For any of these sections, you’ll need a slightly modified approach to finding the total overall area called the AB measurement.

Using the AB Measurement Method to Get Pool Size

  1. This measurement requires two points, A and B. Mark on the deck of the pool at least 4’ out from the edge with a line straight between these points. 
  2. Looking straight at your pool, you’ll want to make sure point A is to the left of point B.  The line between these points should not extend across the pool itself. This puts the AB line at somewhere around 66% of the length.
  3. At the midway point between A and B, measure how far the distance is to the pool’s edge to form a triangle. 
  4. From the triangle’s point, you’ll want to move clockwise and make a second point around 3 feet away and continue doing so every 3 feet. 
  5. From each of these new points, you’ll need to take a measurement back to both points A and B, respectively. If you number your points, your measurements might look something like “A1 = 5.5 feet”, meaning from point A to the tip of the first triangle point you made, “1”, is a distance of 5.5 feet. 
  6. You’ll need to continue this measurement all the way around the pool for both A and B points. 
  7. Finally, take at least four measurements diagonally from a few of these numbered tips. 

All of these measurements are important in getting a custom pool cover created. It’s also a good idea to take pictures and even draw a scaled sketch of how you took your measurements so that the cover’s manufacturer can get it right for purposes of an initial rough estimate.

How to Measure Pool Size in Gallons

Calculating how much water your pool holds is vital for knowing what size maintenance systems are needed. There are several basic formulas our pool pros use to calculate how much water a pool can hold, depending on the shape of the pool.

Rectangle Pools 

For a rectangular-shaped pool, use the formula length x width x average depth x 7.48. Length times width provides surface area, and multiplying that by an average depth provides volume in cubic feet. With 7.48 gallons equaling 1 cubic foot, you use that as your multiplier to find out how many gallons of water your pool holds. For example, if you have a 15’ x 30’ pool, with an average depth of 5’, your calculation would be 15 x 30 x 5 x 7.48 = 16,830 gallons of water.

Circular Pools

If you have a circular-shaped pool, the equation starts with π r 2. Consider a 4’-deep pool with 10’ diameter and a radius of 5’. Your figure would look like 3.14 x 52 = 78.5 of surface area x 4’ = 314 sq ft. x 7.48 = 2,349 gallons of water.

Oval-Shaped Pools

Oval pools follow the formula of length x width x average depth x 5.9. For a 15’ x 30’ pool with an average depth of 5’, your equation would be - 15 x 30 x 5 x 5.9 = 13,275 gallons of water.

swimming pool with a retractable cover

 

How to Measure Pool Size for Cover

When you have a regular shape like our olympic pool in the example above, getting a cover to match is fairly straightforward. Simply plug in your length and width and you should be able to find a standard size pool cover. When your pool is an irregular shape, you’ll need to follow the steps we outlined to get the AB measurement for pool size. This method will provide the measurements needed to get a custom pool cover for your pool’s unique shape.  

What Size Pool Pump Do I Need?

The size of the pump needed for your pool is based on several factors, some of which follow government standards for safety and hygiene. The size of your pool’s pipes, how many right-angle bends are in the pipe, vertical lift, and even the distance from the pump to the pool are all variables that need to be accounted for. These variables help to produce a figure known as head loss. Your pump will need to produce a minimum flow rate in order to meet sanitation requirements. 

To get this figure, you’ll need to look up the building code in your area as the requirements can differ. For example, Florida Building Code R4101.20 dictates that “the entire design of matched components must have significant capacity to provide a complete turnover of pool water within 12 hours or less”. 

To get the minimum flow rate, you’d take your volume in gallons and divide it by the specified turnover rate in minutes. If your pool holds 16,830 gallons of water and we use 12 hours to get 720 minutes, your formula would be 16,830 ÷ 720 minutes = 23.375 gallons per minute is the minimum flow rate required for your pool pump. 

Pro Tip: If your pool requires a pump with at least 23.375 GPM of flow rate, it’s generally best to go with a slightly bigger pump in order to compensate when components like the filter become dirty and the flow rate is impeded.

How to Size Pool Heaters Like a Pro

Solar heaters, electric pool heaters, gas—oh my? As with most things when it comes to pools, you’ll have a choice of a variety of pool heaters and the size of the heater depends on the type you choose. Each has its own advantages and disadvantages but all rely on how quickly they can heat your pool as indicated by their British Thermal Unit (BTU) rating. 

A general rule is to have at least 50,000 BTUs per 10,000 gallons of water. So with a 30,000-gallon pool, you’d want 150,000 BTUs. 

How to Size Pool Filters for Any Size Pool

There are several different types of filters available that all offer unique advantages. There’s generally not a best filter for every application but there are certainly pros and cons. Like your home’s air conditioning unit filter, pool filters differ in their level of performance. 

Some filters will remove smaller particles, others are easier to clean or install, some are more expensive, etc. The most important thing to remember is to at least get the minimum requirement met based on the flow rate and filtration rate. The max filtration rate is set based on the filter media type such as sand filters or cartridge filters. 

As a general example, if you want a rapid sand filter with a max filtration rate of 3 and you have a 90 GPM pool pump, you’d divide 90 by 3 to get 30 square feet as the minimum size filter to do the job. As with pumps, it’s always a good idea to default to a size up in order to keep your pool its cleanest.

Get Your Florida Pool Professionally Maintained

At JOMO Pool Service, our sole mission is to make sure your pool is operating at peak performance. We take the time to fully evaluate your existing system, take accurate measurements, and develop a plan of action to maintain a healthy and balanced system. Contact our team or call us at 904-222-0809 now to schedule an appointment.