Square Feet to Cubic Feet Calculator
Square feet measures area, and cubic feet measures volume, so there's no fixed ratio between them: you also need a depth. Enter your area and a depth to get cubic feet and cubic yards.
How to calculate square feet to cubic feet
Square feet alone can't convert to cubic feet, you need a depth or thickness too. Convert the depth to feet (divide inches by 12), then multiply it by the area in square feet to get the volume in cubic feet.
Cubic feet = Area (ft²) × Depth (ft)
Worked example
A 100 ft² patio getting a 4-inch layer of concrete.
- Depth = 4 in ÷ 12 = 0.333 ft
- Volume = 100 ft² × 0.333 ft
Result: 100 square feet at 4 inches deep = 33.3 cubic feet (1.23 cubic yards)
Frequently asked questions
How do I convert square feet to cubic feet?
You can't convert directly, square feet is area and cubic feet is volume. Multiply your area in square feet by the depth in feet to get cubic feet. For example, 100 ft² at 4 inches (0.333 ft) deep is 100 × 0.333 = 33.3 ft³.
Why isn't there a fixed square feet to cubic feet conversion factor?
Because area and volume measure different things. The same 100 ft² area could hold 8.3 ft³ at 1 inch deep or 100 ft³ at 12 inches deep, the depth is what makes the difference.
How many cubic feet are in 1 square foot at 1 foot deep?
Exactly 1 cubic foot. A 1 ft² area with a 1 ft depth is 1 ft × 1 ft × 1 ft = 1 ft³.
How do I convert cubic feet to cubic yards?
Divide the cubic feet by 27, since one cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft).
What depth should I use for concrete, mulch, or gravel?
Concrete slabs are typically 4 inches deep, mulch beds 2 to 3 inches, and gravel paths 2 to 4 inches. Check your project's spec, then enter that depth above to get the volume.