Calculate liquid gallons per square foot and total volume from area and depth, or recover base area from volume and depth, with US and imperial units.
How to use this tool
- Choose volume from area and depth, or base area from volume and depth.
- Enter the selected area or volume input and identify its unit.
- Enter actual liquid depth, not outside wall height or rim height.
- Select Calculate and read US liquid gallons and imperial gallons under their distinct labels.
Formula and unit basis
US gal/ft² = depth(ft) × 1728/231. Total US gallons = base area(ft²) × US gal/ft². Reverse area = volume(ft³) ÷ depth(ft). Imperial gallons use exactly 4.54609 L per gallon.
Worked examples
One inch over 100 ft² is 62.337662 US gallons. In reverse mode, 1,000 US gallons at 3 ft depth requires an equivalent constant base area of 44.560185 ft².
Assumptions and interpretation
This is a geometric liquid-depth calculation for a constant footprint, not a paint coverage-rate calculator. Use internal wetted dimensions and actual water depth. Irregular slopes, steps and displacement need separate volume adjustments. No collection efficiency, water-treatment or structural loading recommendation is supplied.
Project guides
- Rainfall Depth to Stored Water: Roof Collection and Loss Factors
- Pool Footprint from Gallons and Depth: Water Level, Slopes and Displacement
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Explore Construction calculators or return to the GreenCalc home page for other subjects.
Frequently asked questions
Can square feet be converted into gallons without depth?
No. Area requires a liquid depth to determine a volume.
Are US and imperial gallons identical?
No. The tool reports them separately using their defined volume conversions.
Does this estimate paint coverage?
No. It models geometric liquid depth over a constant footprint. Paint coverage depends on the product and application conditions.