Pool Volume Calculator
Knowing your pool's volume is essential for proper chemical dosing, heater sizing, and filter selection. This pool volume calculator handles rectangular pools, giving you gallons, liters, and cubic feet from length, width, and average depth measurements.
Advertisement
Calculator
See your Pool Volume Calculator results
Enter your email to unlock results — free forever.
No spam, ever. Unsubscribe at any time.
Advertisement
Formula
Gallons = L × W × Avg Depth × 7.48
Length, width, and average depth in feet are multiplied to get cubic feet of water. Multiplying by 7.48 converts cubic feet to US gallons (1 cubic foot = 7.48 gallons). Multiply by 3.785 to convert gallons to liters.
How to use the Pool Volume Calculator
- 1
Enter your pool length (ft)
Value should be in ft.
- 2
Enter your pool width (ft)
Value should be in ft.
- 3
Enter your average depth (ft)
Value should be in ft.
- 4
Read your results instantly
Results update in real time as you type.
Advertisement
Finding Average Depth
For a pool with a shallow end and a deep end, average depth = (shallow depth + deep depth) / 2. A common residential pool has a 3-foot shallow end and 8-foot deep end, giving an average depth of 5.5 feet. For a pool with a gradual slope and no flat bottom, measure at several points and average them. The average depth method works well for rectangular pools; irregular shapes require more complex calculations.
Using Volume for Chemical Dosing
Pool chemical doses are always expressed per 10,000 gallons of pool water. Knowing your pool's exact volume lets you dose chlorine, shock, pH adjusters, and algaecides precisely. Over-dosing wastes chemicals and can irritate swimmers; under-dosing leaves the pool unprotected. Recheck your volume calculation seasonally as evaporation and refilling change water chemistry over time.
Tips & Insights
Measure When Full
Calculate your pool volume when it's at its normal operating level. Note the gallon count on your pool's water meter when you initially fill it — this is your most accurate volume reference.
Use Volume for Heater Sizing
Pool heater output (in BTUs) determines how fast it can raise water temperature. A rough rule: 1 BTU raises 1 gallon by 1°F per hour. For a 20,000-gallon pool, a 200,000 BTU heater can raise temperature 10°F in about 10 hours.
Account for Features
Spas, attached hot tubs, and water features add volume to your system. If your pool has a spa, measure it separately (usually 250–500 gallons) and add it to the pool volume for total system volume.
Worked Examples
Standard Backyard Pool
16,830 gallons — dose chemicals per 10,000-gallon increments, so use 1.683x the standard dose.
Lap Pool
17,952 gallons — a standard 75-foot lap pool requires similar chemical volumes to a residential pool.
Advertisement
Frequently Asked Questions
How many gallons is a typical backyard pool?
A typical residential pool (15×30 ft, 5 ft average depth) holds about 16,875 gallons. Most backyard pools range from 10,000 to 30,000 gallons.
How do I calculate pool volume for an irregular shape?
Divide the pool into rectangular and circular sections. Calculate each section's volume separately and add them together. For kidney or freeform shapes, use length × average width × average depth as an approximation.
How much does it cost to fill a pool with water?
Water rates vary widely, but at an average US rate of $0.005 per gallon, a 20,000-gallon pool costs about $100 to fill. Check with your local water utility — some offer a pool-fill rate discount.
How often should I test pool water?
Test pH and free chlorine at least 2–3 times per week during swimming season. Test alkalinity, calcium hardness, and stabilizer monthly. After heavy rain or high bather load, test and adjust immediately.
How much chlorine do I need for my pool?
Maintain free chlorine at 1–3 ppm. Add 1–2 oz of liquid chlorine (10% sodium hypochlorite) per 1,000 gallons daily as a general starting point, then adjust based on test results.
Advertisement