Gallons per Square Foot Calculator
Convert an area and depth into a water/liquid volume in gallons.
Work out how many gallons of water sit on (or are needed to flood) a given area at a chosen depth — useful for ponds, flooded slabs, irrigation and coverage estimates.
How the Math Works
The Gallons per Square Foot Calculator uses a straightforward volume conversion formula: gallons = area (ft²) × depth (ft) × 7.48052. This calculation works by first multiplying the surface area in square feet by the depth in feet to get the volume in cubic feet. The result is then multiplied by the conversion factor 7.48052, which represents the number of gallons in one cubic foot, to convert the volume into gallons. For example, if you have a surface area of 100 square feet and a depth of 0.5 feet, the calculation would be 100 × 0.5 × 7.48052 = 374.026 gallons.
Practical Applications
To use this calculator practically, simply enter the area measurement in square feet and the desired depth in feet (or convert inches to feet by dividing by 12). The calculator will instantly provide the volume in gallons. This tool is invaluable for projects involving liquid coverage, such as determining how much water is needed to flood a specific area for construction testing, calculating the amount of liquid fertilizer required for a garden bed, or estimating water usage for landscape irrigation planning. You can also work backwards: if you know how many gallons you have available and the area to cover, divide by (7.48052 × depth) to find the achievable depth.
Day-to-Day Use
In everyday life, this calculator helps you make informed decisions about water usage and project planning. Whether you're filling a fish tank, calculating water volume for a swimming pool, determining how much mulch or soil is needed (by converting gallons to cubic feet), or estimating water consumption for outdoor projects, this tool eliminates guesswork. Homeowners use it to plan irrigation systems, estimate water bills, or determine container sizes for plants. It's also useful for DIY projects involving liquid materials, helping you avoid costly over-purchases or project delays due to insufficient materials.
Worked example
100 ft² at 1 in deep → 100 × (1/12) × 7.48052 = 62.3 US gallons.
FAQ
How many gallons in a cubic foot?
7.48052 US gallons (about 28.32 liters).