Pool Volume Calculator/20x40 Rectangular Pool Volume Calculator
Standard Specs: 20 ft Width x 40 ft Length x 4.5 ft Avg Depth
20x40 Rectangular Pool Volume Calculator
Large Estate & Commercial Pool Capacity (28,000–35,000 Gallons)
A 20x40 rectangular pool with a 4.5-foot average depth holds approximately 27,000 gallons (102,200 liters). With an 8.5-foot diving bowl, volume reaches 36,000 gallons. Accurate volume calculations prevent costly chemical under-dosing.
Water Capacity Dashboard
Adjust average water depth if your pool has a different wall height.
Average Water Depth3 feet
US Gallons
18,000
Total liquid capacity
Metric Liters
68,137
International standard
Water Weight
75.1 Tons
150,120 lbs total load
Chemical Dosage Starting Numbers for 18,000 Gallons
Salt to Reach 3,200 PPM
13 Bags (40-lb)
Cal-Hypo Routine Shock
1.8 lbs (68-73%)
Liquid Chlorine Shock
1.4 Gallons (12.5%)
20x40 Pool Water Dynamics & Load Specs
• Water Weight: ~225,000 lbs (over 112 US tons of hydraulic weight)
• Salt Startup: 720 lbs (18 bags of 40-lb pool salt)
• Weekly Shock Requirement: 2.7 to 3.5 lbs Calcium Hypochlorite
Plumbing and Filtration Infrastructure
Large 20x40 estate pools require minimum 2-inch PVC plumbing and dual skimmers to ensure adequate water circulation across the 800 sq ft surface area.
Popular Pool Dimension Volume Calculators
Frequently Asked Questions: 20x40 Rectangular Pool Volume Calculator
A 20x40 pool with a 3ft shallow end and an 8ft deep end (5.5ft average depth) holds approximately 33,000 gallons.
A 20x40 pool typically consumes 3 to 5 three-inch trichlor tablets per week, plus 3 lbs of shock weekly during summer swim season.