Pool Volume Calculator

Calculate the volume of any swimming pool in gallons and liters. Works for rectangular, circular, oval, kidney-shaped, and L-shaped pools. Essential for chemical treatment, pool heater sizing, and water costs.

🏊️ Pool🏗️ Gallons = Length x Width x Average Depth x 7.48 (rectangular)

Pool shape

Length (ft)

Width (ft)

Shallow end depth (ft)

Deep end depth (ft)

Please enter valid values.

Formula & Reference

Variable	Formula	Units
Pool Volume Calculator	Gallons = Length x Width x Average Depth x 7.48 (rectangular)	gallons + liters

Step-by-Step Examples

Example 1

Standard Rectangular Pool

32x16 ft, 3-ft shallow end, 8-ft deep end.

Avg depth = (3+8)/2 = 5.5 ft
Volume = 32 x 16 x 5.5 x 7.481 = 21,100 gallons
Shape factor = 1.0 for rectangular

✓ ~21,100 gallons

Example 2

Round Above-Ground Pool

18-ft diameter circle, uniform 4-ft depth.

Shape factor = 0.785 (circle)
Volume = 18 x 18 x 4 x 0.785 x 7.481 = 7,646 gallons
Standard 18-ft round pool: approx 7,500-8,000 gallons

✓ ~7,646 gallons

Example 3

Kidney-Shaped Pool

30x15 ft, 3.5 ft to 7 ft depth.

Avg depth = 5.25 ft
Kidney factor = 0.85
Volume = 30 x 15 x 5.25 x 0.85 x 7.481 = 15,068 gallons

✓ ~15,068 gallons

Real-World Applications

🏊️

Pool Owners

Calculate chemical doses, fill time, and heater size from pool volume.

💰

Pool Service

Accurate volume is essential for proper chlorine, algaecide, and pH chemical dosing.

⚡️

Heater Sizing

BTU heater requirements are calculated directly from pool volume and target temperature rise.

🚰

Water Costs

Estimate fill costs from municipal water rates and pool volume.

Common Mistakes to Avoid

⚠️

Using average depth incorrectly for pools with variable depths

For pools with sloping bottoms, average depth = (shallow end + deep end) / 2. If the pool has a flat deep section and a step-change slope, calculate each section separately.

⚠️

Forgetting the shape factor for non-rectangular pools

Oval and round pools multiply by 0.785 (pi/4). Kidney and irregular pools by approximately 0.85. Using rectangular formula for round pools overestimates volume by 27%.

⚠️

Not recalculating after adding a spa or raised floor

If your pool has a spa, sun shelf, or raised floor section, calculate each section separately and add together.

Frequently Asked Questions

How many gallons in a typical backyard pool? ▾

Typical residential pool: 15,000-30,000 gallons. Small plunge pool: 5,000-10,000 gallons. Large pool (20x40+): 30,000-50,000 gallons. Above-ground pools: 5,000-15,000 gallons.

How long to fill a swimming pool? ▾

At 5 gallons per minute (typical garden hose), filling a 20,000-gallon pool takes about 66 hours (nearly 3 days). A 1-inch water supply line at 10 gpm takes about 33 hours. Always check with your municipality before filling.

How much does it cost to fill a swimming pool? ▾

At $0.005 per gallon (average municipal water rate), a 20,000-gallon pool costs about $100 to fill. Local rates vary significantly; check your water bill for your rate. Add $50-$150 for startup chemicals.

How do I size a pool heater? ▾

Rule of thumb: BTU = (Pool volume in gallons x 8.33 lbs/gal x desired temp rise in deg F) / 24 hours. A 20,000-gallon pool raised 20 deg F needs about 138,750 BTU/hr. Choose the next size up heater.

How much chlorine for my pool? ▾

1-2 ppm free chlorine is the ideal range. For initial startup or shocking: add 1 lb of granular chlorine per 10,000 gallons to raise level 1 ppm. Always test water before and after chemical additions.