Pool Volume & Chlorine Calculator

Pool volume by shape

The formulas this calculator uses (in US gallons):

• Rectangular: Length × Width × Avg Depth × 7.48
• Round: Diameter² × Avg Depth × 5.9
• Oval: Length × Width × Avg Depth × 6.7
• Kidney / irregular: (Width A + Width B) × Length × Avg Depth × 3.38

Average depth = (shallow end depth + deep end depth) ÷ 2. For a typical 14×28 ft inground with 3' shallow and 6' deep, avg depth is 4.5 ft, volume is ~13,200 gallons.

Chlorine math for shock

"Shock" means raising free chlorine to 10× the combined chloramine level (or a minimum of 10-20 ppm) to break apart chloramines and oxidize organics. 1 lb of calcium hypochlorite (cal hypo) raises 10,000 gallons by about 7.5 ppm. Standard shock doses:

• Standard shock (every 1-2 weeks): 1 lb cal hypo per 10,000 gallons
• After heavy rain or pool party: 2 lb per 10,000 gallons
• Algae bloom (visible green): 3-4 lb per 10,000 gallons
• Pool opening (post-winter): 5 lb per 10,000 gallons

Maintenance chlorine targets

• Free chlorine: 1-3 ppm, ideally 2-3
• Combined chlorine (chloramines): Below 0.5 ppm. If higher, shock.
• pH: 7.2-7.8. Above 7.8 weakens chlorine effectiveness.
• Total alkalinity: 80-120 ppm. Buffers pH swings.
• Calcium hardness: 200-400 ppm. Low = corrosion. High = scale.
• Cyanuric acid (stabilizer): 30-50 ppm for outdoor pools. Protects chlorine from UV.

Salt vs traditional chlorine

Saltwater pools STILL use chlorine — they just generate it from salt via a chlorinator cell. Pros:

• Gentler on skin and eyes (salinity ~3,000 ppm — about 1/10th of seawater).
• No chlorine smell in the water.
• Lower ongoing cost after initial salt + cell investment.

Cons: salt cells cost $400-800 to replace every 3-7 years; salt corrodes some pool hardware (stone coping, ladders); requires more careful water chemistry to protect the cell.

Algae prevention

• Run the pump 8-12 hours/day in summer. Stagnant water + warmth = bloom in 24 hours.
• Brush walls weekly. Algae attaches to surfaces; brushing breaks it loose.
• Phosphate remover if you can't maintain consistent chlorine — phosphates feed algae.
• Algaecide (PolyQuat 60): Weekly preventive dose, especially in shaded pools.

Common chemistry mistakes

• Adding shock during the day: UV destroys most of it. Always shock at dusk or after sundown.
• Mixing different chlorine types: Cal hypo + trichlor tablets create explosive reactions. Never add to the same skimmer at the same time.
• Adding pH chemicals too fast: Pour slowly into a running return jet, never the skimmer. Wait 30 minutes between chemicals.
• Skipping alkalinity: Adjust alkalinity to range BEFORE adjusting pH. Without alkalinity buffer, pH bounces.
• Over-using stabilizer: Cyanuric acid above 80 ppm "locks up" chlorine — it stays present but stops sanitizing.