Square Feet to Cubic Feet Calculator
Important: there is no direct conversion from square feet to cubic feet. Square feet measure area, cubic feet measure volume, and you must also know the depth or thickness to go from one to the other. This calculator does exactly that: area times depth equals volume.
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cubic feet (ft3)
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cubic yards (yd3)
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cubic meters (m3)
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cubic inches (in3)
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US gallons
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depth
Quick reference: 100 square feet at common depths
| Depth | Cubic feet | Cubic yards |
|---|---|---|
| 1 in | 8.3333 | 0.30864 |
| 2 in | 16.6667 | 0.61728 |
| 3 in | 25.0000 | 0.92593 |
| 4 in | 33.3333 | 1.23457 |
| 6 in | 50.0000 | 1.85185 |
Formula: volume (ft3) = area (ft2) x depth (ft). One inch is 1/12 of a foot, so 100 sq ft at 4 in = 100 x 4/12 = 33.3333 ft3.
Worked examples
Concrete patio: a 10 x 20 ft patio is 200 sq ft. At 4 inches thick: 200 x 4/12 = 66.6667 ft3, which is 66.6667 / 27 = 2.4691 yd3 of concrete to order.
Mulch bed: a 50 sq ft bed at 3 inches deep needs 50 x 3/12 = 12.5 ft3 of mulch. One 2 ft3 bag spread over 50 sq ft gives a depth of 2 / 50 = 0.04 ft = 0.48 in.
Reverse: you have 2 cubic yards of topsoil for a 100 sq ft garden. 2 yd3 = 54 ft3, so depth = 54 / 100 = 0.54 ft = 6.48 in.
How to convert square feet to cubic feet
Square feet measure area (length x width). Cubic feet measure volume (length x width x height). To go from square feet to cubic feet you must supply the missing third dimension: the depth or thickness.
- Measure or decide the area in square feet (length x width in feet).
- Decide the depth in inches, feet, centimeters, or meters.
- Convert the depth to feet (divide inches by 12).
- Multiply: volume in cubic feet = area in square feet x depth in feet.
Example: 100 sq ft x 4 in = 100 x 0.3333 ft = 33.3333 ft3.
Frequently asked questions
Can you convert square feet directly to cubic feet?
No. There is no direct conversion because square feet measure area (two dimensions) and cubic feet measure volume (three dimensions). You must also know the depth or thickness. Only then can you calculate volume as area times depth. Any tool that claims a one-step conversion without asking for depth is misleading.
What is the formula for square feet to cubic feet?
The square feet to cubic feet formula is: volume in cubic feet = area in square feet x depth in feet. If your depth is in inches, divide it by 12 first. Example: 100 sq ft at 4 inches deep = 100 x 4/12 = 100 x 0.3333 = 33.3333 ft3.
How many cubic feet is 100 square feet at 4 inches deep?
33.3333 cubic feet. The same volume equals 1.23457 cubic yards, 0.94389 cubic meters, or 249.35 US gallons.
How do I convert the answer to cubic yards?
Divide cubic feet by 27, because one cubic yard holds 27 cubic feet (3 x 3 x 3). For example: 33.3333 ft3 / 27 = 1.23457 yd3. The calculator shows cubic yards, cubic meters, and gallons automatically.
How do I find the depth if I know the volume and the area?
Use the reverse mode: depth = volume / area. Example: 1 cubic yard (27 ft3) spread over 100 sq ft gives a depth of 27 / 100 = 0.27 ft = 3.24 in. Two cubic yards over the same 100 sq ft give 6.48 in.
How do I convert inches, centimeters, or meters to feet for the depth?
Divide inches by 12, divide centimeters by 30.48, or multiply meters by 3.2808. The calculator accepts depth in inches, feet, centimeters, or meters and converts it to feet for you before multiplying.
Can I enter the area in square yards or square meters?
Yes. The area is converted to square feet first: 1 square yard = 9 square feet, and 1 square meter = 10.7639 square feet. Example: 25 sq m at 10 cm deep = 269.098 ft2 x 0.3281 ft = 88.2867 ft3.
How much concrete do I need for a 200 sq ft patio at 4 inches thick?
200 x 4/12 = 66.6667 cubic feet, which is 66.6667 / 27 = 2.4691 cubic yards. You would order about 2.5 cubic yards from a ready-mix supplier.
How much mulch covers 50 sq ft at 3 inches deep?
50 x 3/12 = 12.5 cubic feet. Bagged mulch is sold in cubic feet, so that is about six 2 ft3 bags. A single 2 ft3 bag spread over 50 sq ft gives a depth of only 0.48 in.
How many cubic meters or gallons are in one cubic foot?
1 cubic foot = 0.028316847 cubic meters (exact: 0.028316846592) = 7.4805 US gallons. Going the other way, 1 US gallon = 0.1337 cubic feet.
What is the difference between this calculator and a square-feet converter?
A square-feet converter only changes area units, for example sq ft to sq yd, sq m, or acres. This tool goes further: it combines area with a depth to produce a volume in cubic feet, cubic yards, cubic meters, and gallons, and it has a reverse mode that finds the depth from a known volume and area.
What if the depth is not even across the whole area?
Use the average depth. The formula stays exact for the average: volume = area x average depth. For rough ground, measure the depth in several spots, average the readings, and enter that average.
Why do contractors order more material than the calculated volume?
Compaction, spillage, and uneven subgrade mean the real need is higher than the exact geometric volume. Concrete is commonly ordered with 5 to 10 percent extra on top of the calculated cubic yards. This calculator gives the exact geometric volume so you can add your own margin.
How many cubic inches are in a cubic foot?
1728. Since 1 foot = 12 inches, a cubic foot is 12 x 12 x 12 = 1728 cubic inches.
Related tools
- Cubic feet to pounds - convert a volume to weight using material density
- Cubic feet to gallons - convert a volume to US or imperial gallons
- Concrete calculator - estimate concrete for slabs, footings, and columns
Scope note: a pure area-unit converter (sq ft to sq yd, sq m, acres) and a square-feet-to-cubic-yards variant are separate tools; this calculator focuses on the honest area-plus-depth path with cubic feet as the primary unit.
Free tool by NRTechStudio