Pool Volume Calculator

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pool volume calculator
Rectangular or SquareCircular / RoundOval
US Gallons (Feet)Liters (Meters)
Results:
function toggleInputs(){var shape=document.getElementById('pool_shape').value;var rowWidth=document.getElementById('row_width');var labelLen=document.getElementById('label_len');if(shape==='round'){rowWidth.style.display='none';labelLen.innerHTML='Diameter:';}else{rowWidth.style.display='table-row';labelLen.innerHTML='Length:';}}function calculatePoolVolume(){var shape=document.getElementById('pool_shape').value;var unitType=document.getElementById('units').value;var len=parseFloat(document.getElementById('input_len').value);var wid=parseFloat(document.getElementById('input_wid').value);var shallow=parseFloat(document.getElementById('input_shallow').value);var deep=parseFloat(document.getElementById('input_deep').value);var showSteps=document.getElementById('showSteps').checked;if(isNaN(len)||isNaN(shallow)||isNaN(deep)){alert('Please fill in all required dimensions.');return;}if(shape!=='round'&&isNaN(wid)){alert('Please enter a width.');return;}var avgDepth=(shallow+deep)/2;var cubicVol=0;var finalVol=0;var labelUnits="";var volUnits="";if(shape==='rect'){cubicVol=len*wid*avgDepth;}else if(shape==='round'){var radius=len/2;cubicVol=Math.PI*Math.pow(radius,2)*avgDepth;}else if(shape==='oval'){cubicVol=len*wid*avgDepth*0.89;}if(unitType==='imperial'){finalVol=cubicVol*7.48;volUnits="Gallons";labelUnits="Cubic Feet";}else{finalVol=cubicVol*1000;volUnits="Liters";labelUnits="Cubic Meters";}document.getElementById('answer').style.display='block';document.getElementById('finalResult').innerHTML=Math.round(finalVol).toLocaleString()+' '+volUnits;var detailText='Average Depth: '+avgDepth.toFixed(2)+' units
';if(showSteps){detailText+='Total Volume: '+cubicVol.toFixed(2)+' '+labelUnits;}document.getElementById('stepDetails').innerHTML=detailText;}

How to Use the Pool Volume Calculator

Maintaining the correct chemical balance in your swimming pool starts with one essential piece of data: total water volume. Our pool volume calculator is designed to help pool owners and professionals quickly estimate the number of gallons or liters required to fill any standard pool shape. Whether you are treating algae, balancing pH, or winterizing, knowing your volume prevents chemical waste and equipment damage.

To get started, follow these simple measurement steps:

1. Determine Shape
Select between Rectangular, Round, or Oval pool shapes. This changes the underlying geometric formula used for calculation.
2. Measure Dimensions
Measure the length, width (if applicable), and diameter in feet or meters. Be sure to measure from the inside walls of the pool, not the coping.
3. Calculate Average Depth
Most pools have a shallow end and a deep end. Enter both depths, and the calculator will automatically find the average for you.

The Math Behind the Pool Volume Calculator

Volume calculations represent three-dimensional space. We first find the cubic area (cubic feet or meters) and then convert that to a liquid measurement. The core formula used for most pools is:

Volume = Surface Area × Average Depth × Conversion Factor

  • Average Depth: Calculated as (Shallow Depth + Deep Depth) / 2.
  • Rectangular Surface Area: Length × Width.
  • Round Surface Area: π × Radius² (where radius is half of the diameter).
  • Conversion Factor (US): 1 cubic foot of water = 7.48 US Gallons.
  • Conversion Factor (Metric): 1 cubic meter of water = 1,000 Liters.

Real-World Calculation Example

Scenario: You have a rectangular backyard pool that is 30 feet long and 15 feet wide. The shallow end is 3 feet deep, and the deep end is 8 feet deep. How many gallons of water are in the pool?

Step-by-step solution:

  1. Calculate Average Depth: (3ft + 8ft) / 2 = 5.5 feet.
  2. Calculate Cubic Area: 30ft (L) × 15ft (W) × 5.5ft (Avg Depth) = 2,475 cubic feet.
  3. Convert to Gallons: 2,475 × 7.48 = 18,513 gallons.
  4. Result: Your pool holds approximately 18,500 gallons of water.

Common Questions

Why is the volume slightly different than the manufacturer's manual?

Manufacturer manuals often provide the volume to the very top of the rim. In practice, pools are filled about 6 inches below the top (to the middle of the skimmer). Our calculator uses the water depth you provide, which is more accurate for chemical dosage.

What if my pool has a variable slope or "hopper" bottom?

For complex shapes like L-shapes or lazy rivers, it is best to break the pool into sections. Calculate the volume of each rectangular part separately and then add the totals together. For hopper bottoms, the "Average Depth" formula provides a close estimate, but you may want to increase the calculated chemical dose slowly.

How much does water weight matter?

Water is heavy! One US gallon weighs about 8.34 lbs. If the example pool above holds 18,500 gallons, the water alone weighs over 154,000 lbs. This is why proper structural support and ground leveling are critical for above-ground pools.

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