How do I calculate the volume of a rectangular pool?

For a rectangular pool: Volume (gallons) = Length × Width × Average Depth × 7.48052. Average depth = (Shallow End + Deep End) / 2. For example, a 20 ft × 40 ft pool with 3 ft shallow end and 8 ft deep end has an average depth of 5.5 ft and holds about 32,834 gallons.

How many gallons does a 12×24 pool hold?

A 12×24 pool with an average depth of 5 ft holds approximately 10,782 gallons (12 × 24 × 5 × 7.48052). With a 3.5 ft shallow end and 7 ft deep end the average depth is 5.25 ft, giving about 11,321 gallons.

How much chlorine do I need to shock my pool?

A standard shock dose uses approximately 1 pound of granular chlorine (calcium hypochlorite) per 10,000 gallons. So a 20,000-gallon pool needs about 2 pounds for a single shock treatment. Always follow the product label for exact dosing.

Pool Volume Calculator

Calculate swimming pool volume in gallons, liters, and cubic feet — plus chemical dosing and heating cost estimates

Pool Dimensions

Pool Shape

Length (ft)

Width (ft)

Shallow End Depth (ft)

Deep End Depth (ft)

Pump Flow Rate (GPM)

Pool Volume 0 gallons

Cubic Feet 0 ft³

Liters 0 L

Surface Area 0 ft²

Water Weight 0 tons

Avg Depth 0 ft

Turnover Time 0 hrs

Chemical Dosing Guide

Dosing amounts are calculated from the pool volume entered in the Calculator tab. Adjust your pool volume there to update these figures.

Current Pool Volume: — gallons

Current Free Chlorine (ppm)

Current pH

Current Total Alkalinity (ppm)

Recommended Chemical Additions

Always add chemicals separately with pump running. Wait 15–30 minutes between additions.

Heating Parameters

Estimate the cost to heat your pool from current to target temperature.

Current Water Temp (°F)

Target Temp (°F)

Heater Type

Natural Gas Price ($/therm)

Heater Efficiency (%)

Heating Cost $0

BTU Required 0 BTU

Temp Rise 0 °F

Therms Used —

kWh Used —

Time to Heat —

Pool Volume 0 gal

Heat Loss vs Useful Heat

Pool Volume Formulas

Rectangle V = L × W × D_avg × 7.48 D_avg = (Shallow + Deep) / 2

Oval V = π/4 × A × B × D × 7.48 A = long axis, B = short axis

Round V = π/4 × D² × depth × 7.48 D = diameter

Kidney V = 0.85 × L × W × D × 7.48 0.85 = kidney shape factor

Ideal Water Chemistry Ranges

Parameter	Ideal Range	Low Impact	High Impact
Free Chlorine	1–3 ppm	Algae, bacteria growth	Eye/skin irritation
pH	7.4–7.6	Corrosion, chlorine loss	Scale, cloudy water
Total Alkalinity	80–120 ppm	pH instability	Cloudy water, scale
Calcium Hardness	200–400 ppm	Corrosion, etching	Scale, cloudy water
Cyanuric Acid (CYA)	30–50 ppm	Rapid chlorine loss	Chlorine lock
Total Dissolved Solids	< 2,000 ppm	—	Corrosion, reduced effectiveness

Chemical Dosing Reference

Chemical	Purpose	Dose	Notes
Granular Chlorine (65%)	Shock / raise chlorine	1 lb per 10,000 gal	Pre-dissolve, add at dusk
Liquid Chlorine (10%)	Regular chlorination	10 oz per 10,000 gal	Add with pump running
Algaecide (60%)	Prevent / treat algae	16 oz per 10,000 gal	Weekly prevention dose
Sodium Carbonate (pH Up)	Raise pH	6 oz per 10,000 gal	Raises pH 0.2 units
Muriatic Acid (pH Down)	Lower pH	16 oz per 10,000 gal	Lowers pH ~0.2 units
Sodium Bicarbonate (Alk Up)	Raise alkalinity	1.5 lb per 10,000 gal	Raises TA ~10 ppm
Cyanuric Acid (Stabilizer)	Protect chlorine from UV	1 lb per 10,000 gal	Raises CYA ~10 ppm

Common Pool Sizes

Pool Size	Shape	Avg Depth	Approx Gallons
12 × 24 ft	Rectangle	5 ft	10,800
16 × 32 ft	Rectangle	5.5 ft	21,000
20 × 40 ft	Rectangle	5.5 ft	32,800
18 ft round	Round	4 ft	7,650
24 ft round	Round	4.5 ft	15,300
15 × 30 ft	Oval	5 ft	13,400

How to Calculate Pool Volume

Select your pool shape — Choose from Rectangle, Oval, Round, L-Shape, or Kidney. Each shape uses a specific volume formula.

Enter your dimensions — Measure length, width, and depth in feet. For pools with a sloped bottom, use the average of the shallow and deep end depths.

Review the volume — The calculator shows gallons, cubic feet, and liters. It also calculates surface area and water weight.

Check chemical dosing — Use the Chemical Dosing tab to get recommended amounts for chlorine, pH adjustment, and algaecide based on your pool's volume.

Pool Terminology

Gallons (US) — The standard unit for pool volume in the US. 1 gallon = 3.785 liters = 0.134 cubic feet.

Turnover Rate — How long it takes the pump to circulate the entire pool volume once. Ideal is 6–8 hours.

GPM — Gallons Per Minute. Typical residential pool pumps deliver 40–75 GPM.

Shock — Adding a large dose of chlorine (usually 1 lb per 10,000 gal) to oxidize contaminants and kill algae.

Cyanuric Acid (CYA) — A stabilizer that protects chlorine from UV degradation. Too much causes chlorine lock.

Total Alkalinity (TA) — The water's ability to resist pH changes (buffering capacity). Target 80–120 ppm.

BTU — British Thermal Unit. The heat required to raise 1 lb of water by 1°F. Used to size pool heaters.

COP — Coefficient of Performance. For heat pumps, COP 5 means 5 BTUs of heat for every 1 BTU of electricity used.

Frequently Asked Questions

How do I measure my pool's average depth?

For a pool with a sloped bottom, average depth = (shallow end depth + deep end depth) / 2. For example, a pool with a 3.5 ft shallow end and 8 ft deep end has an average depth of 5.75 ft. For pools with a uniform depth (above-ground pools), the average depth equals the actual depth.

How often should I shock my pool?

Most pools should be shocked once per week during swim season, or after heavy use, a rainstorm, or when the water appears cloudy or green. Use 1 lb of granular chlorine (calcium hypochlorite, 65%) per 10,000 gallons. Always shock at dusk to prevent UV degradation.

What pump flow rate do I need?

Select a pump that can turn over your pool volume in 6–8 hours. For a 20,000-gallon pool: 20,000 / (7 hrs × 60 min) = 47.6 GPM minimum. Most residential pools use a 1–1.5 HP pump delivering 40–65 GPM. Variable-speed pumps are more energy-efficient and often required by code.

How much does it cost to heat a pool?

To raise a 20,000-gallon pool from 65°F to 80°F requires about 2,098,800 BTU. At 85% efficiency with gas at $1.35/therm: roughly $33.32 for the initial heat-up. Daily maintenance costs are lower since you only compensate for heat loss (typically 1–3°F overnight).

How do I calculate the volume of an irregular-shaped pool?

For a kidney-shaped pool, multiply length × width × average depth × 7.48 × 0.85 (the kidney shape factor). For freeform pools, divide the pool into recognizable sections (rectangles, ovals), calculate each section's volume separately, and add them together.