Gallons per Square Foot Calculator
Convert between area, volume, and liquid coverage for pools, tanks, and containers
Calculate Gallons per Square Foot
Base area of the container or surface
Height or depth of liquid in container
Calculation Results
Formula: 1 cubic foot = 7.48052 US gallons
Calculation: Gallons per sq ft = Height (ft) × 7.48052
Height: 0.00 feet
Coverage Analysis
Practical Examples
Swimming Pool Water Volume
Pool: 20 ft × 10 ft = 200 sq ft area
Depth: 4 feet average
Calculation: 4 ft × 7.48052 = 29.92 gal/sq ft
Total volume: 200 sq ft × 29.92 gal/sq ft = 5,984 gallons
Water Tank Storage
Tank base: 8 ft × 8 ft = 64 sq ft area
Height: 6 feet
Calculation: 6 ft × 7.48052 = 44.88 gal/sq ft
Total volume: 64 sq ft × 44.88 gal/sq ft = 2,872 gallons
Reverse Calculation: Find Area
Given: 1,000 gallons of water, 3 feet depth
Gallons per sq ft: 3 ft × 7.48052 = 22.44 gal/sq ft
Required area: 1,000 gal ÷ 22.44 gal/sq ft = 44.6 sq ft
Volume Conversion Reference
1 Cubic Foot =
7.48052 US gallons
28.3168 liters
1,728 cubic inches
1 US Gallon =
3.78541 liters
231 cubic inches
0.133681 cubic feet
1 Square Foot =
144 square inches
0.092903 square meters
Common Applications
Calculation Tips
Measure depth at multiple points for irregular containers
Account for displacement by objects in the container
Use average depth for sloped bottoms
Consider freeboard space in tanks and pools
Why Use This Calculator?
Instant Results
Real-time calculations as you type
Multiple Units
Supports US/Imperial gallons, liters, meters, feet
Precise Conversions
Uses exact 7.48052 conversion factor
Free & No Registration
100% free tool, no sign-up required
Mobile-Friendly
Works perfectly on all devices
Comprehensive Results
Multiple unit conversions displayed
Understanding Gallons per Square Foot
What is Gallons per Square Foot?
Gallons per square foot is a measurement of liquid volume per unit area. It represents how many gallons of liquid would cover one square foot of surface area at a specific depth. This measurement is crucial for calculating water volumes in pools, tanks, and other containers. Whether you're planning a swimming pool installation, sizing a water storage tank, or determining aquarium capacity, understanding gallons per square foot helps you accurately estimate liquid volumes.
Key Formula
Gallons per sq ft = Height (ft) × 7.48052
Total Volume = Area (sq ft) × Gallons per sq ft
This formula uses the conversion factor that 1 cubic foot equals 7.48052 US gallons. The conversion is derived from the fact that 1 US gallon equals 231 cubic inches, and 1 cubic foot contains 1,728 cubic inches (12 × 12 × 12).
Why This Matters
Accurate volume calculations are essential for proper chemical treatment in pools, correct sizing of pumps and filters, water conservation planning, and cost estimation for filling operations. Using gallons per square foot simplifies complex volume calculations into an easy-to-understand measurement that works for containers of any size.
Common Applications
- •Swimming pool water volume - Calculate gallons for pool filling, chemical treatment dosing, and heating requirements
- •Water tank and storage capacity - Size residential, commercial, and agricultural water storage systems
- •Aquarium and pond volume - Determine water volume for proper fish stocking and filtration sizing
- •Industrial liquid storage - Calculate capacity for chemical storage, wastewater treatment, and process tanks
- •Hot tubs and spas - Accurately measure water volume for chemical balance and heating calculations
- •Irrigation reservoirs - Plan water storage for agricultural and landscape irrigation systems
- •Rainwater collection - Size cisterns and collection systems for sustainable water management
Essential Conversion Factors
Volume Conversions:
• 1 cubic foot = 7.48052 US gallons
• 1 cubic foot = 6.22884 Imperial gallons
• 1 US gallon = 3.78541 liters
• 1 cubic foot = 28.3168 liters
• 1 cubic meter = 264.172 US gallons
Area Conversions:
• 1 square foot = 144 square inches
• 1 square meter = 10.7639 square feet
• 1 square yard = 9 square feet
Real-World Calculation Examples
Rectangular Pool
Dimensions: 20 ft × 15 ft
Average Depth: 5 feet
Area: 300 square feet
Gal/sq ft: 5 × 7.48 = 37.4
Total: 11,220 gallons
Cylindrical Tank
Diameter: 10 feet (radius 5 ft)
Height: 8 feet
Area: π × 5² = 78.5 sq ft
Gal/sq ft: 8 × 7.48 = 59.84
Total: 4,697 gallons
Hot Tub
Dimensions: 7 ft × 7 ft
Average Depth: 3.5 feet
Area: 49 square feet
Gal/sq ft: 3.5 × 7.48 = 26.18
Total: 1,283 gallons
Common Use Cases for Gallons per Square Foot Calculator
Swimming Pool Volume Calculation
Accurately calculate pool water volume for chemical treatment, heating costs, and filling expenses. Essential for pool maintenance professionals and homeowners planning pool construction or renovation. Works for rectangular, oval, and free-form pool shapes.
Popular for: In-ground pools, above-ground pools, Olympic-size pools, lap pools
Water Tank Capacity Planning
Size residential, agricultural, and industrial water storage tanks. Perfect for rainwater harvesting systems, well water storage, emergency water supplies, and irrigation reservoirs. Calculate capacity for rectangular, cylindrical, and custom tank designs.
Popular for: Cisterns, holding tanks, pressure tanks, bulk storage
Aquarium and Fish Pond Volume
Determine exact water volume for proper fish stocking rates, filtration system sizing, and medication dosing. Critical for maintaining healthy aquatic environments in home aquariums, commercial fish farms, and decorative koi ponds.
Popular for: Freshwater aquariums, saltwater tanks, koi ponds, fish hatcheries
Hot Tub and Spa Sizing
Calculate water capacity for hot tubs, spas, and therapeutic pools. Essential for proper chemical balance, sanitizer dosing, and heating equipment selection. Helps estimate operating costs and water replacement needs.
Popular for: Jacuzzis, whirlpool baths, therapy pools, resort spas
Industrial Liquid Storage
Size process tanks, chemical storage vessels, wastewater treatment systems, and industrial cooling systems. Accurate volume calculations ensure proper equipment sizing and regulatory compliance for hazardous and non-hazardous liquid storage.
Popular for: Chemical plants, food processing, manufacturing, water treatment
Irrigation System Design
Calculate water requirements for agricultural irrigation, landscape watering, and greenhouse operations. Plan reservoir sizing, pump capacity, and water budget for efficient crop production and landscape maintenance.
Popular for: Farm irrigation, golf courses, parks, commercial landscapes
How to Use the Gallons per Square Foot Calculator
Step-by-Step Instructions
Select Calculation Method
Choose "Area + Height → Volume" if you know the base area and want to calculate volume, or "Volume + Height → Area" if you know the volume and want to find the required area.
Enter Your Measurements
Input the area or volume and the height/depth of your container. The calculator supports multiple units including square feet, square meters, gallons, liters, feet, inches, and more.
Get Instant Results
The calculator instantly provides gallons per square foot, total volume, and area. Additional conversions in liters, cubic inches, square yards, and gallons per square meter are also shown.
Analyze Coverage
Review the coverage analysis to understand if your measurements are suitable for your application, whether it's a pool, tank, aquarium, or industrial container.
💡 Pro Tip
For irregular-shaped containers or pools, measure the depth at multiple points and use the average depth for more accurate results. Always add 10-15% extra capacity for safety margins in tank and pool applications.
Frequently Asked Questions
How do you calculate gallons per square foot?
To calculate gallons per square foot, multiply the height or depth (in feet) by 7.48052. This conversion factor represents the number of US gallons in one cubic foot. For example, if your pool is 4 feet deep, the gallons per square foot would be 4 × 7.48052 = 29.92 gallons per square foot.
How many gallons of water are in a square foot?
The number of gallons in a square foot depends on the depth of the water. One cubic foot of water equals 7.48052 US gallons. So if you have water that is 1 foot deep over an area of 1 square foot, you have 7.48 gallons. At 2 feet deep, you'd have 14.96 gallons per square foot, and so on.
How do I calculate pool water volume in gallons?
To calculate pool water volume: First, measure the surface area of your pool in square feet (length × width for rectangular pools). Then measure the average depth in feet. Multiply the area by the depth to get cubic feet, then multiply by 7.48052 to convert to gallons. For example, a 20ft × 10ft pool with 4ft average depth: 200 sq ft × 4 ft = 800 cubic feet × 7.48052 = 5,984 gallons.
What is the conversion factor from cubic feet to gallons?
The standard conversion factor is 1 cubic foot = 7.48052 US gallons. This is based on the definition that 1 US gallon equals 231 cubic inches, and 1 cubic foot equals 1,728 cubic inches. Therefore: 1,728 ÷ 231 = 7.48052 gallons per cubic foot. Note that Imperial (UK) gallons use a different conversion: 1 cubic foot = 6.22884 Imperial gallons.
How do I calculate water tank capacity?
For a rectangular or square tank, multiply the length × width to get the base area in square feet. Multiply this by the height in feet to get cubic feet, then multiply by 7.48052 to convert to gallons. For cylindrical tanks, use the formula: Volume = π × radius² × height. Convert the result from cubic feet to gallons using the same 7.48052 multiplier.
What's the difference between US gallons and Imperial gallons?
US gallons and Imperial (UK) gallons are different measurements. One US gallon equals 3.785 liters, while one Imperial gallon equals 4.546 liters. This means 1 Imperial gallon = 1.20095 US gallons. Our calculator uses US gallons by default, but you can select Imperial gallons from the volume unit dropdown for conversions.
How accurate is the gallons per square foot calculator?
Our calculator uses the precise conversion factor of 7.48052 gallons per cubic foot, which is accurate to 5 decimal places. The results are as accurate as the measurements you provide. For best results, measure dimensions carefully and use the appropriate units. For irregular shapes, consider breaking the area into sections and calculating separately, then adding the results.
Can I use this calculator for irregular-shaped pools or tanks?
Yes, but with some adjustments. For irregular shapes, divide the pool or tank into regular sections (rectangles, circles, etc.), calculate the volume for each section separately, and add them together. For pools with varying depths, use the average depth: (shallow end depth + deep end depth) ÷ 2. This method provides a good approximation for most practical applications.
Why should I account for displacement in my calculations?
Objects inside a container (like pool steps, rocks in an aquarium, or equipment in a tank) displace water, reducing the actual volume. For accuracy, subtract approximately 5-10% from your calculated volume to account for displacement. This is especially important for aquariums with decorations, hot tubs with seating, or tanks with internal components.
How do I calculate gallons per square foot for paint coverage?
While this calculator is primarily designed for liquid volume in containers, it can help estimate paint coverage. However, paint coverage is typically measured differently (square feet per gallon rather than gallons per square foot). Most paints cover 250-400 square feet per gallon at recommended thickness. For thin coatings, you might use the calculator by entering a very small depth (like 0.01 feet for approximate film thickness).
Pro Tips for Accurate Gallons per Square Foot Calculations
📏Measurement Best Practices
- •
Use Multiple Measurements
For irregular containers, measure at several points and calculate the average to improve accuracy. This is especially important for pools with sloped bottoms or variable depths.
- •
Account for Displacement
Subtract 5-10% for pool steps, seats, decorations, equipment, or any objects that displace water. This prevents overestimation and ensures accurate chemical dosing.
- •
Measure in the Same Units
Take all measurements in the same unit system (all metric or all imperial) to reduce conversion errors. The calculator handles unit conversions automatically.
- •
Consider Freeboard
Don't fill tanks to the very top. Leave 6-12 inches of freeboard space for safety, expansion, and overflow prevention.
💡Advanced Calculation Tips
- •
Complex Shapes
For L-shaped or custom pools, divide into simple rectangles or circles, calculate each section separately, then add the volumes together for total capacity.
- •
Sloped Bottoms
For pools with sloped bottoms, use the formula: Average Depth = (Shallow End + Deep End) ÷ 2. This provides a good approximation for volume calculations.
- •
Round vs. Oval Pools
For round pools, use π × radius². For oval pools, use π × length/2 × width/2. The calculator handles rectangular shapes automatically.
- •
Temperature Effects
Water volume changes slightly with temperature (expands when heated). For precise applications, measure at expected operating temperature.
⚠️Important Safety Considerations
Chemical Safety: Accurate volume calculations are essential for proper chemical dosing. Overestimating can lead to insufficient treatment, while underestimating can cause dangerous over-chlorination or pH imbalances.
Structural Load: Water weighs approximately 8.34 lbs per gallon. Always verify that structures can support the calculated water weight (about 62.4 lbs per cubic foot).