Sq Ft to Cubic Feet Calculator
Cubic Feet
Cubic Yards
3D Volume Diagram
InteractiveHow to Convert Square Feet to Cubic Feet
Square feet measures area — a flat, two-dimensional surface. Cubic feet measures volume — a three-dimensional space. To calculate volume, you need to add a third dimension: depth, height, or thickness.
The Core Formula
Volume Formula
Key FormulaExample: 200 sq ft × 0.5 ft (6 inch slab) = 100 cubic feet
When Depth Is Given in Inches
Divide the depth in inches by 12 to convert to feet before multiplying. A 3-inch deep mulch layer over 500 sq ft: 500 × (3 ÷ 12) = 500 × 0.25 = 125 cubic feet. Our calculator handles this unit conversion automatically.
Converting to Cubic Yards
Divide cubic feet by 27 to get cubic yards (since 1 cubic yard = 3ft × 3ft × 3ft = 27 cubic feet). Concrete and fill dirt are typically sold by the cubic yard. 81 cubic feet ÷ 27 = 3 cubic yards.
Common Depth-to-Volume Reference
| Material | Typical Depth | Per 100 Sq Ft | Per 1,000 Sq Ft |
|---|---|---|---|
| Mulch | 3 inches | 2.08 cu ft | 20.83 cu ft |
| Topsoil | 6 inches | 4.17 cu ft | 41.67 cu ft |
| Concrete slab | 4 inches | 2.78 cu ft | 27.78 cu ft |
| Gravel base | 4 inches | 2.78 cu ft | 27.78 cu ft |
| Sand fill | 2 inches | 1.39 cu ft | 13.89 cu ft |
| Poured asphalt | 3 inches | 2.08 cu ft | 20.83 cu ft |
To convert cubic feet to cubic yards (for ordering), divide by 27. For mulch over 1,000 sq ft at 3 inches: 25 cu ft ÷ 27 = 0.93 cu yd — order 1 cubic yard.
Practical Applications for Volume Calculation
Concrete Slabs & Foundations
Before pouring concrete, calculate the volume in cubic feet, then divide by 27 for cubic yards. Concrete suppliers sell by the cubic yard. A 20 ft × 20 ft patio at 4 inches depth: 400 × 0.333 = 133 cubic feet = 4.94 cubic yards. Order 5.5 yards including waste.
Mulch & Landscaping Beds
Garden beds and landscaping areas need mulch at 2–4 inch depths. Calculate the bed area in square feet, choose depth, and find cubic feet. Most bags are 2 cubic feet; bulk orders are by the cubic yard.
Swimming Pool & Water Features
Pool volumes are calculated in cubic feet, then converted to gallons (1 cu ft = 7.48 gallons). A pool 20 ft × 40 ft × 5 ft average depth = 4,000 cu ft = 29,922 gallons to fill.
Fill Dirt & Excavation
When filling low spots or grading land, calculate the volume in cubic feet. Divide by 27 for cubic yards to order the correct number of truckloads (typically 10–14 cu yd per dump truck).
Frequently Asked Questions
Square feet (ft²) measures 2-dimensional area — the surface of a floor, wall, or plot of land. Cubic feet (ft³) measures 3-dimensional volume — the amount of space inside a container, the depth of fill, or the capacity of a room. Cubic feet = square feet × height/depth.
Multiply the square footage by the depth or height in feet. If the depth is in inches, divide by 12 first. Example: 300 sq ft × (6 inches ÷ 12) = 300 × 0.5 = 150 cubic feet.
10 × 10 = 100 sq ft. Depth = 4 inches = 4/12 = 0.333 ft. Volume = 100 × 0.333 = 33.33 cubic feet = 1.23 cubic yards. Order at least 1.5 yards for waste.
500 × (3/12) = 500 × 0.25 = 125 cubic feet. 125 ÷ 27 = 4.63 cubic yards. Order 5 cubic yards for coverage plus minimal waste.
1 cubic foot = 7.48052 US gallons. So 100 cubic feet × 7.48052 = 748 gallons. Useful for pool and tank capacity calculations.
Exactly 27 cubic feet. Since 1 yard = 3 feet, 1 cubic yard = 3 × 3 × 3 = 27 cubic feet. Always divide cubic feet by 27 when ordering bulk materials sold by the cubic yard.
Yes. Measure the room's square footage (length × width), then multiply by the ceiling height in feet. A 12 × 15 ft room with 9 ft ceilings: 180 × 9 = 1,620 cubic feet of air volume. This is used for HVAC sizing and air exchange rate calculations.
For most garden beds, 2–4 inches of mulch is ideal. 2 inches suppresses weeds and retains moisture; 3–4 inches is better for moisture retention in dry climates. Avoid piling mulch against tree trunks (keep it 6 inches away). Calculate: area × depth in feet = cubic feet needed.