Free Pool Volume Calculator Online
Knowing the volume of your swimming pool isn’t just about satisfying curiosity it’s about ensuring your water chemistry is safe, maintenance is efficient, and your pool stays swim-ready all season. Whether you have a rectangular pool, circular pool, or irregular shape, using a pool volume calculator makes this a simple calculation. You can determine how many gallons your pool holds, what chemicals to use, and how much water you’ll need to fill or refill it.
This comprehensive guide breaks down everything you need to know about measuring pool volume, from calculating surface area to applying the right formula for your pool shape. Let’s dive into the water.
Pool Volume Calculator
Why Use a Pool Volume Calculator?
Accurately calculating your pool volume is essential for maintaining a clean, safe swimming environment. Improper water balance whether from too much chlorine or not enough salt can cause health issues, damage surfaces, and wear out equipment prematurely. A pool volume calculator solves this by telling you exactly how much water your pool holds, often in gallons, cubic feet, or liters.
Benefits of knowing your pool volume:
- Avoid chemical imbalances by dosing the correct amount of chlorine, pH adjusters, or algaecides
- Calculate pool salt needs using a pool salt calculator
- Plan for water deliveries or cost estimates in local currency
- Manage pool maintenance more efficiently
- Estimate water costs, refill needs, and total surface area
Key Measurements Needed for Pool Calculations
Before using a calculator, gather these essential dimensions:
- Length (in feet or meters)
- Width
- Depth – both shallow end depth and deep end depth
- Radius or diameter for circular pools
- Shape of the pool
You’ll also need to decide on units: feet, meters, gallons, or liters. Some calculators offer a drop-down menu for unit conversion.
How to Calculate Average Depth
If your pool has both a shallow end and a deep end, use this formula to get the average depth: $$Average Depth=Shallow End Depth+Deep End Depth2\text{Average Depth} = \frac{\text{Shallow End Depth} + \text{Deep End Depth}}{2}Average Depth=2Shallow End Depth+Deep End Depth$$
Example:
If the shallow end is 3 feet and the deep end is 9 feet: $$Average Depth=3+92=6 feet\text{Average Depth} = \frac{3 + 9}{2} = 6 \text{ feet}Average Depth=23+9=6 feet$$
This value is crucial for calculating total pool volume, especially in rectangular pools or oval pools.
Pool Volume Formulas by Shape
Each pool shape requires a specific formula. Below are the most common ones with LaTeX-formatted equations:
Rectangular Pool
$$Volume (gallons)=Length×Width×Average Depth×7.5\text{Volume (gallons)} = \text{Length} \times \text{Width} \times \text{Average Depth} \times 7.5Volume (gallons)=Length×Width×Average Depth×7.5$$
The number 7.5 represents how many gallons are in a cubic foot of water.
Circular Pool
$$Volume (gallons)=π×(Diameter2)2×Average Depth×7.5\text{Volume (gallons)} = \pi \times \left( \frac{\text{Diameter}}{2} \right)^2 \times \text{Average Depth} \times 7.5Volume (gallons)=π×(2Diameter)2×Average Depth×7.5$$
This is ideal for circular pools or spas.
Oval Pool
$$Volume (gallons)=π×Length×Width×Average Depth×5.9\text{Volume (gallons)} = \pi \times \text{Length} \times \text{Width} \times \text{Average Depth} \times 5.9Volume (gallons)=π×Length×Width×Average Depth×5.9$$
Use 5.9 instead of 7.5 to account for curved sides.
Kidney-Shaped Pool
$$Volume (gallons)=(Length+Width)×Average Depth×Area Factor\text{Volume (gallons)} = \left( \text{Length} + \text{Width} \right) \times \text{Average Depth} \times \text{Area Factor}Volume (gallons)=(Length+Width)×Average Depth×Area Factor$$
Area Factor varies depending on irregular shape – generally between 0.45–0.65.
Sample Calculation: Rectangular Pool
Let’s calculate the pool volume for a 30 ft long, 15 ft wide rectangular pool with a shallow end depth of 3 ft and a deep end of 9 ft.
Step 1: Average Depth $$Average Depth=3+92=6 feet\text{Average Depth} = \frac{3 + 9}{2} = 6 \text{ feet}Average Depth=23+9=6 feet$$
Step 2: Pool Volume $$Volume=30×15×6×7.5=20,250 gallons\text{Volume} = 30 \times 15 \times 6 \times 7.5 = 20,250 \text{ gallons}Volume=30×15×6×7.5=20,250 gallons$$
Converting Units
Not all calculators default to US gallons. If you get the volume in cubic feet, here’s how to convert it:
Cubic Feet to Gallons
$$=Cubic Feet×7.48\text{Gallons} = \text{Cubic Feet} \times 7.48Gallons=Cubic Feet×7.48$$
Feet to Meters
$$1 foot=0.3048 meters1 \text{ foot} = 0.3048 \text{ meters}1 foot=0.3048 meters$$
Liters to Gallons
$$US Gallons=Liters3.785\text{US Gallons} = \frac{\text{Liters}}{3.785}US Gallons=3.785Liters$$
Pool Shapes and Their Surface Area
Knowing the surface area helps calculate evaporation rates, heating costs, and more.
Square or Rectangular Surface Area
Surface Area=Length×Width\text{Surface Area} = \text{Length} \times \text{Width}Surface Area=Length×Width
Circular Surface Area
$$Surface Area=π×r2\text{Surface Area} = \pi \times r^2Surface Area=π×r2$$
Tools and Features of a Pool Calculator
A robust pool volume calculator offers:
- Support for rectangular, circular, oval, irregular pools
- Input fields for all dimensions (length, width, depth, radius)
- Automatic calculation of surface area, volume, and chemical doses
- Outputs in gallons, liters, or cubic meters
- Integration with pool salt calculator and maintenance tools
Common Mistakes to Avoid
Here’s where pool owners go wrong:
- Ignoring water displacement from features like benches or fountains
- Using inconsistent units (mixing feet and meters)
- Forgetting to average depth for uneven floors
- Estimating rather than measuring dimensions
- Skipping measurements for attached spas or hot tubs
Example: Calculating for an Oval Pool
An oval pool is 20 feet long, 10 feet wide, and has a shallow depth of 3 feet and a deep end of 8 feet.
Step 1: Average Depth $$Average Depth=3+82=5.5 feet\text{Average Depth} = \frac{3 + 8}{2} = 5.5 \text{ feet}Average Depth=23+8=5.5 feet$$
Step 2: Volume $$Volume=π×20×10×5.5×5.9≈20,393 gallons\$$ $$text{Volume} = \pi \times 20 \times 10 \times 5.5 \times 5.9 \approx 20,393 $$ $$\text{ gallons}Volume=π×20×10×5.5×5.9≈20,393 gallons$$
Maintenance and Cost Calculations
Your pool’s volume influences more than just water:
- Chemical dosage: Chlorine, pH, algaecide
- Water bills: Know how many gallons or cubic feet you’re paying for
- Heater size: BTU capacity depends on water volume
- Filter requirements: Filter size is rated by gallons per minute (GPM)
- Salt purchase price variance: Based on pool size and desired salinity
Summary Table of Formulas
| Pool Type | Formula (Gallons) |
|---|---|
| Rectangular | $$L×W×Avg Depth×7.5L \times W \times \text{Avg Depth} \times 7.5L×W×Avg Depth×7.5$$ |
| Circular | $$π×(D/2)2×Avg Depth×7.5\pi \times (D/2)^2 \times \text{Avg Depth} \times 7.5π×(D/2)2×Avg Depth×7.5$$ |
| Oval | $$π×L×W×Avg Depth×5.9\pi \times L \times W \times \text{Avg Depth} \times 5.9π×L×W×Avg Depth×5.9$$ |
| Kidney/Irregular | $$(L+W)×Avg Depth×Area Factor(L + W) \times \text{Avg Depth} \times \text{Area Factor}(L+W)×Avg Depth×Area Factor$$ |
| Avg. Depth | $$Shallow+Deep2\frac{\text{Shallow} + \text{Deep}}{2}2Shallow+Deep$$ |
| Cubic Feet to Gallons | $$Cubic Feet×7.48\text{Cubic Feet} \times 7.48Cubic Feet×7.48$$ |
| Salt Requirement | $$Volume×PPM1200\frac{\text{Volume} \times \text{PPM}}{1200}1200Volume×PPM$$ |
Final Thoughts
A pool volume calculator is an essential tool for any pool owner, builder, or maintenance team. By calculating the exact water volume, you save money, prevent maintenance issues, and improve the overall swimming experience. Whether you own a circular pool, a kidney shape, or a simple rectangular pool, a few basic measurements and formulas will help you keep everything balanced—chemically and financially.
If you haven’t measured your pool depth, width, or radius, now’s the time. The simple calculations you make today can save you gallons of trouble tomorrow.