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Pool Volume Calculator

Calculate pool volume and chemical needs

Units

Pool Volume

21064

gallons

Liters

79726

Cubic Feet

2816

Water Cost

$105

Fill Time (garden hose)

~39 hours (1.6 days)

Chemical Requirements (Weekly)

Chlorine

16.9 oz

Liquid or tablets

Shock Treatment

2.1 lbs

Weekly shock

Algaecide

8.4 oz

Prevention dose

pH Balancer

3.2 lbs

As needed

Common Pool Sizes

Small (12x24 ft)~10,000 gallons
Medium (16x32 ft)~20,000 gallons
Large (20x40 ft)~30,000 gallons
Olympic (82x164 ft)~660,000 gallons

Volume Formulas

Rectangle:

Length × Width × Avg Depth × 7.48

Oval:

Length × Width × Avg Depth × 5.9

Round:

Diameter² × Avg Depth × 5.9

Kidney/Freeform:

Length × Width × Avg Depth × 6.4

Volume Comparison

Gallons21.1k
Liters79.7k
Cubic Feet2.8k

Frequently Asked Questions

Q

How do I calculate my pool volume in gallons?

For rectangular pools: Length × Width × Average Depth × 7.48. For round pools: Diameter² × Depth × 5.9. For oval pools: Length × Width × Depth × 5.9. These formulas give you the volume in gallons.

Q

How many gallons is an average pool?

Average inground pools hold 15,000-30,000 gallons. A typical 16×32 ft pool with 5 ft average depth holds about 19,200 gallons. Above-ground pools typically hold 5,000-15,000 gallons.

Q

How long does it take to fill a pool?

With a standard garden hose (9 GPM), filling a 20,000-gallon pool takes about 37 hours or 1.5 days of continuous flow. Using multiple hoses or a fire hydrant fill service can reduce this significantly.

Q

Why is knowing pool volume important?

Pool volume determines proper chemical dosing. Too little chlorine won't sanitize; too much can irritate skin and damage equipment. Accurate volume ensures proper pH balance, algae prevention, and safe swimming conditions.

Q

How much does it cost to fill a pool with water?

At average US water rates ($0.004-$0.006 per gallon), filling a 20,000-gallon pool costs $80-$120. Some areas charge more. Municipal pools may qualify for reduced rates or use hydrant fill services.

Example Calculations

1Rectangular Pool (32 × 16 ft)

Inputs

ShapeRectangle
Length32 ft
Width16 ft
Shallow End3 ft
Deep End8 ft

Result

Pool Volume21,064 gallons
Liters79,727
Cubic Feet2,816
Fill Time~39 hours (1.6 days)
Water Cost$105

Average depth = (3 + 8) / 2 = 5.5 ft. Cubic feet = 32 × 16 × 5.5 = 2,816. Gallons = 2,816 × 7.48 = 21,064. Fill time at 9 GPM = 21,064 / 540 = 39 hours.

2Round Pool (18 ft diameter)

Inputs

ShapeRound
Diameter18 ft
Shallow End3 ft
Deep End5 ft

Result

Pool Volume7,614 gallons
Liters28,821
Cubic Feet1,018
Fill Time~14.1 hours (0.6 days)
Water Cost$38

Average depth = (3 + 5) / 2 = 4 ft. Radius = 18 / 2 = 9 ft. Cubic feet = π × 9² × 4 = 1,018. Gallons = 1,018 × 7.48 = 7,614. Fill time at 9 GPM = 7,614 / 540 = 14.1 hours.

Formulas Used

Rectangular Pool Volume

Gallons = Length × Width × Avg Depth × 7.48

Calculates volume for a rectangular pool by multiplying dimensions in feet to get cubic feet, then converting to gallons.

Where:

Length= Pool length in feet
Width= Pool width in feet
Avg Depth= (Shallow End + Deep End) / 2 in feet
7.48= Gallons per cubic foot conversion factor

Round Pool Volume

Gallons = π × (Diameter / 2)² × Avg Depth × 7.48

Calculates volume for a circular pool using the area of a circle times depth, converted to gallons.

Where:

Diameter= Pool diameter in feet
Avg Depth= (Shallow End + Deep End) / 2 in feet
π= 3.14159

Fill Time Estimate

Fill Hours = Gallons / (9 × 60)

Estimates fill time using a standard garden hose flow rate of 9 gallons per minute.

Where:

Gallons= Pool volume in gallons
9= Garden hose flow rate in GPM

Understanding Pool Volume Calculations

Knowing your pool's exact volume is the starting point for proper maintenance. Chemical manufacturers base their dosing instructions on gallons of water, so an inaccurate estimate can lead to under-treated or over-treated water.

Pool shape affects volume calculations significantly. Freeform and kidney-shaped pools require adjustment factors (typically 0.85) because they have less water than a rectangle of the same dimensions. Always measure at multiple points for the most accurate depth average.

For variable-depth pools, calculate the average depth by adding the shallow end and deep end depths, then dividing by two. This works well for pools with a gradual slope. Pools with sudden drop-offs may need section-by-section calculations for accuracy.

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Last Updated: Feb 12, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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