Pool Calculator
Free Pool Calculator for water tank & vessels projects. Enter dimensions to get material lists and cost estimates. Get results you can export or share.
Formula
Volume = L x W x AvgDepth x 7.48 (gallons)
Pool volume is calculated by multiplying the surface area by the average depth to get cubic feet, then converting to gallons by multiplying by 7.48. Average depth is the mean of shallow and deep end depths. Circular pools use pi x radius^2 for area. Chemical dosing scales proportionally with volume.
Worked Examples
Example 1: Standard Residential Pool
Problem: Calculate the volume of a 30x15 ft rectangular pool with 3.5 ft shallow end and 6 ft deep end.
Solution: Average depth = (3.5 + 6) / 2 = 4.75 ft\nVolume = 30 x 15 x 4.75 = 2,137.5 cu ft\nGallons = 2,137.5 x 7.48 = 15,989 gal\nFill time = 15,989 / 540 = 29.6 hours
Result: 15,989 gallons, approximately 30 hours to fill with a garden hose
Example 2: Circular Above-Ground Pool
Problem: Calculate volume for a 24-foot diameter round pool with a uniform 4-foot depth.
Solution: Radius = 12 ft\nAverage depth = (4 + 4) / 2 = 4 ft\nVolume = pi x 144 x 4 = 1,809.6 cu ft\nGallons = 1,809.6 x 7.48 = 13,536 gal
Result: 13,536 gallons
Frequently Asked Questions
How do I calculate the volume of my swimming pool in gallons?
For a rectangular pool, multiply length by width by average depth (all in feet) and then multiply by 7.48 to convert cubic feet to gallons. Average depth is the shallow end depth plus the deep end depth divided by two. For a 30x15 foot pool with 3.5 ft shallow and 6 ft deep ends, the average depth is 4.75 ft, giving 30 x 15 x 4.75 x 7.48 = 15,979 gallons. Round or oval pools use the same concept but with circular area formulas.
How much chlorine does my pool need?
A typical pool needs about 2 pounds of liquid chlorine (sodium hypochlorite) per 10,000 gallons per week to maintain 1-3 ppm free chlorine. Granular chlorine (calcium hypochlorite at 65% strength) requires about 2 ounces per 10,000 gallons to raise chlorine by 1 ppm. After heavy rain, high bather loads, or algae blooms, shock treatment requires 1 pound of granular shock per 10,000 gallons to superchlorinate. Always test before adding chemicals and never mix different chemicals together.
How long does it take to fill a swimming pool?
A standard garden hose delivers about 9 gallons per minute (540 gallons per hour). At this rate, a 15,000-gallon pool takes approximately 28 hours to fill. A 3/4-inch hose may deliver 15-25 GPM with good water pressure. Some homeowners use two hoses simultaneously to cut fill time in half. Contact your water utility before filling, as some charge sewer fees on all metered water and may offer a fill rate discount if notified in advance.
How many BTUs are needed to heat a pool by one degree?
It takes approximately 8.34 BTU to raise one gallon of water by one degree Fahrenheit. A 20,000-gallon pool requires about 166,800 BTU per degree. A typical 400,000 BTU pool heater would raise this pool about 2.4 degrees per hour, assuming no heat loss. In practice, surface evaporation, wind, and nighttime cooling cause significant heat loss, so a pool cover is essential. Solar covers alone can raise water temperature by 10-15 degrees in sunny climates.
What formula does Pool Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.