Knowing how to work out the pool water volume is essential information for every pool owner. If you’re lucky, the pool builder has supplied you with the pool water volume so you don’t need to work out the volume yourself. If you don’t know the volume please follow our pool water volume calculator below.
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Why Know the Pool Water Volume?
The volume of water in your pool is important information for correctly maintaining the water chemistry of your pool. You need to know the water volume to calculate how much chemicals must be added to the pool. All pool chemical manufacturers specify in the instructions the amount of chemical to add to the pool based on the volume of water in the pool.
When selecting a pool pump, filter, salt chlorinator or water heater you will need to correctly size the appliance to the size of the pool. The more water in the pool, the larger the pump, filter or heater.
If you are purchasing a pool cover you will need to know the area of your pool. The area is the volume divided by the average depth.
When you fill the swimming pool you may want to calculate how long it’s going to take from your home water supply. Simply divide the volume of your pool by the hose water flow rate to give the number of hours to fill the pool.
Maybe you want to order a water delivery to your property to fill the pool. You will need to order water to the nearest 100 gallons or litres. You will be able to calculate how much it is going to cost.
How Many Gallons in the Pool?
Calculating the volume of a pool is easy if you know the pool’s dimensions and the geometry equation for volume. These dimensions are easiest for a square or rectangular pool and most difficult for a curved pool.
Here are some useful numbers for your calculations.
One cubic foot of water has 7.5 gallons or 28.31 litres.
Determine the total number of gallons the pool holds by multiplying the cubic feet measurement by 7.5 to get the volume in gallons (or by 28.31 to get litres).
One cubic foot of water weighs 62.4 pounds.
One gallon of water weighs 8.33 pounds.
How Many Litres in the Pool?
If you live outside the USA you will want to know how many litres of water instead of gallons.
To convert from cubic feet to litres multiply by 28.31
Volume (litres) = length x width x average depth x 28.31
Example
Volume (litres) = 30ft x 15ft x 5ft x 28.31 = 63,697 litres
Calculate the Average Depth of a Pool
A swimming pool has a variable depth when a shallow end slopes into a deep end. You will need to calculate the average depth of the pool.
Average Depth = (Shallow depth + Deep depth) / 2
Add the shallow end depth and deep end depth together first. Then divide the sum by two to give the average depth.
Example
Average Depth = ( 3ft + 6ft ) / 2 = 4.5ft
Calculate the Volume of a Rectangular Shaped Pool
A rectangular pool’ geometry is easy to calculate.
Volume (litres) = length x width x average depth x 28.31
Volume (gallons) = length x width x average depth x 7.5
These measurements are in feet to give the number of cubic feet.
Example
Volume (litres) = 24ft x 12ft x 4ft x 28.31 = 32,613 litres
Volume (gallons) = 24ft x 12ft x 4ft x 7.5 = 8,640 gallons
Calculate the Volume of a Round Shaped Pool
A circular or round pool’s geometry is easy to calculate with the following formula.
The dimensions are in imperial measurements ie feet.
Volume (litres) = radius x radius x average depth x 3.14 x 28.31
Volume (gallons) = radius x radius x average depth x 3.14 x 7.5
Example
Volume (litres) = 10ft x 10ft x 5ft x 3.14 x 28.31 = 44,446 litres
Volume (gallons) = 10ft x 10ft x 5ft x 3.14 x 7.5 = 11,775 gallons
Calculate the Volume of a Round Hot Tub
A round or circular hot tub’s geometry is easy to calculate with the following formula.
Volume (litres) = radius x radius x average depth x 3.14 x 28.31
Volume (gallons) = radius x radius x average depth x 3.14 x 7.5
Example
Volume (litres) = 5ft x 5ft x 3ft x 3.14 x 28.31 = 6,667 litres
Volume (gallons) = 5ft x 5ft x 3ft x 3.14 x 7.5 = 1,766 gallons
Please read: Hot Tub Chemicals for Sensitive Skin
Calculate the Volume of an Oval Shaped Pool
An oval pool’s geometry is relatively easy to calculate with the following formula.
The dimensions are in imperial measurements (i.e. feet).
Volume (litres) = length x width x average depth x 28.31 x 3.14 / 4
Volume (gallons) = length x width x average depth x 7.5 x 3.14 / 4
Example
Volume (litres) = 30ft x 15ft x 5ft x 28.31 x 3.14 / 4 = 50,000 litres
Volume (gallons) = 30ft x 15ft x 5ft x 7.5 x 3.14 / 4 = 13,246 gallons
Calculate Volume of Kidney Shaped Pool
A kidney shape pool’s geometry is more complex but can be calculated with the following formula
Volume (litres) = length x (short width + long width) x 0.45 x avg depth x 28.31
Volume (gallons) = length x (short width + long width) x 0.45 x avg depth x 7.5
Example
Volume (litres) = 30ft x (10ft + 15ft) x 0.45 x 5ft x 28.31 = 47,773 litres
Volume (gallons) = 30ft x (10ft + 15ft) x 0.45 x 5ft x 7.5 = 12,656 gallons
Conclusion
Not knowing the pool water volume is one of the most common pool maintenance mistakes. It makes it difficult to work out how much chemicals to add to a pool. And adding the wrong amount of chemicals results in unbalanced water chemistry. Adding too much chemical can be difficult to remedy without draining water from the pool and refilling it.
