Cubic feet of a cylinder
To find the cubic feet of a cylinder, measure the radius and the height in feet and compute V = π × r² × h. A cylinder with a 3 ft radius and a 6 ft height holds π × 9 × 6 = 169.65 cubic feet. If you measured in inches, find the cubic inches and divide by 1,728.
Contents
Cubic feet = π × r² × h with r and h in feet. With r = 3 ft and h = 6 ft: π × 9 × 6 = 169.65 ft³ (6.283 yd³, 1,269 US gallons).
The calculator above accepts the radius or the diameter in any unit, including inches for one measurement and feet for the other, and shows the result in cubic feet with cubic yards and gallons alongside. It applies the same cylinder volume formula used everywhere on this site.
The cubic feet formula and its variants
Volume is the area of the circular base times the height. When both lengths are in feet, the answer comes out directly in cubic feet. The other forms below are the same formula with the unit conversion built in.
| You have | Cubic feet |
|---|---|
| radius and height in feet | π × r² × h |
| diameter and height in feet | π × d² × h ÷ 4, or d² × h × 0.7854 |
| radius and height in inches | π × r² × h ÷ 1,728 |
| diameter in inches, height in feet | d² × h × 0.005454 |
| radius and height in meters | π × r² × h ÷ 0.0283168 |
The mixed-unit factor 0.005454 comes from π ÷ 4 ÷ 144: the diameter in inches is squared, and one square foot holds 144 square inches. It is rounded to four significant figures and suits round columns, posts and sonotube forms, which are sized by diameter in inches and poured to a depth in feet.
How to calculate the cubic feet of a cylinder
- MeasureTake the diameter (or radius) and the height. For capacity, measure inside the walls.
- Convert to feetDivide inches by 12. A measurement of 2 ft 6 in becomes 2.5 ft; 3 ft 4 in becomes 3.333 ft.
- Find the radiusHalve the diameter.
- MultiplyCompute π × r² × h. The result is in cubic feet.
- Convert if neededDivide by 27 for cubic yards, multiply by 7.48052 for US gallons, or multiply by 28.317 for liters.
Worked examples
A tank measured in feet
A tank is 6 ft across and 8 ft tall. The radius is 3 ft, the base area is π × 3² = 28.274 ft², and the volume is 28.274 × 8 = 226.19 ft³. In cubic yards that is 226.19 ÷ 27 = 8.378 yd³; in US gallons, 226.19 × 7.48052 = 1,692 gallons; in cubic meters, 6.405 m³.
Feet and inches together
A planter measures 2 ft 6 in across inside and 3 ft 4 in deep. Convert to decimal feet: 2.5 ft and 3 + 4 ÷ 12 = 3.3333 ft. The radius is 1.25 ft, so V = π × 1.25² × 3.3333 = 16.36 ft³. That is 0.606 yd³ of soil, or 463 L.
Diameter in inches, depth in feet
A round column form is 10 in across and 4 ft deep. One route: convert the diameter to feet (10 ÷ 12 = 0.8333 ft, radius 0.41667 ft), then V = π × 0.41667² × 4 = 2.182 ft³. The other route: convert the depth to inches (48 in), compute π × 5² × 48 = 3,769.9 in³, and divide by 1,728 to get the same 2.182 ft³. The shortcut gives 10² × 4 × 0.005454 = 2.182 ft³ as well.
The typical yield printed on an 80 lb bag of premixed concrete is about 0.60 ft³, so this form needs about 2.182 ÷ 0.60 = 3.6 bags, rounded up to 4. The concrete cylinder calculator adds a waste margin and counts bags for several holes at once.
Cubic inches of a cylinder
Small objects are easier in cubic inches. A can 6 in across and 10 in tall holds π × 3² × 10 = 282.74 in³, which is 282.74 ÷ 1,728 = 0.1636 ft³. Divide the cubic inches by 231 instead, and you get 1.224 US gallons.
From meters to cubic feet
A drum is 0.6 m across and 1.2 m tall. V = π × 0.3² × 1.2 = 0.33929 m³. One cubic foot is 0.0283168 m³, so the drum holds 0.33929 ÷ 0.0283168 = 11.98 ft³. For metric capacity in liters, see the cylinder volume in liters guide.
Cubic feet per foot of height
For round columns, pipes and tanks, it helps to know how much one foot of length holds. Each value is π × (d ÷ 24)² for a diameter d in inches, computed with full-precision π. Multiply by the height or length in feet.
| Diameter | ft³ per foot | yd³ per foot | US gal per foot |
|---|---|---|---|
| 4 in | 0.0873 | 0.00323 | 0.653 |
| 6 in | 0.1963 | 0.00727 | 1.469 |
| 8 in | 0.3491 | 0.01293 | 2.611 |
| 10 in | 0.5454 | 0.02020 | 4.080 |
| 12 in | 0.7854 | 0.02909 | 5.875 |
| 14 in | 1.0690 | 0.03959 | 7.997 |
| 16 in | 1.3963 | 0.05171 | 10.445 |
| 18 in | 1.7671 | 0.06545 | 13.219 |
| 24 in | 3.1416 | 0.11636 | 23.501 |
| 30 in | 4.9087 | 0.18181 | 36.720 |
| 36 in | 7.0686 | 0.26180 | 52.877 |
| 48 in | 12.5664 | 0.46542 | 94.003 |
A 12 in diameter gives 0.7854 ft³ per foot: π ÷ 4, since the cylinder fits exactly inside a one-foot cube. A 24 in diameter gives four times as much, π ft³ per foot.
From cubic feet to cubic yards and gallons
Cubic feet are the working unit for small jobs, but bulk materials such as ready-mix concrete, gravel and mulch are usually sold by the cubic yard. Divide cubic feet by 27 to get cubic yards. For liquids, multiply cubic feet by 7.48052 to get US gallons. The cylinder volume in gallons page has a full capacity chart and the shortcuts for working straight from inches.
| From cubic feet to | Do this |
|---|---|
| cubic yards | divide by 27 (exact) |
| cubic inches | multiply by 1,728 (exact) |
| US gallons | multiply by 7.48052 |
| liters | multiply by 28.316846592 (exact) |
| cubic meters | multiply by 0.028316846592 (exact) |
To know how heavy those cubic feet are, multiply by the density: water is about 62.43 lb per cubic foot. The cylinder weight calculator does this for water, concrete, steel and other materials.
Common mistakes
- Mixing inches and feet. A 10 in diameter and a 4 ft depth multiplied as they stand give π × 5² × 4 = 314.2, which is neither cubic feet nor cubic inches. Convert first.
- Writing 2 ft 6 in as 2.6 ft. Six inches is half a foot: 2.5 ft. Divide the inches by 12.
- Dividing cubic inches by 12. One cubic foot is 12 × 12 × 12 = 1,728 in³, not 12 in³.
- Using the diameter as the radius. The radius is squared, so the error is a factor of four.
- Dividing cubic feet by 9 for cubic yards. Nine converts square feet to square yards; volume needs 27.
Quick check: a cylinder 1 ft across holds about 0.79 ft³ per foot of height, a little less than a one-foot cube.
FAQ
How do I calculate cubic feet of a cylinder?
Put the radius and the height in feet, then compute π × r² × h. If you measured in inches, compute the volume in cubic inches and divide by 1,728, the number of cubic inches in a cubic foot.
How do I find cubic feet of a cylinder if the radius is 3 ft and the height is 6 ft?
V = π × 3² × 6 = π × 54 = 169.65 ft³. That is 6.283 cubic yards (÷ 27) and 1,269 US gallons (× 7.48052).
How do I find the height of a cylinder given the volume and the radius?
Divide the volume by the area of the base: h = V ÷ (π × r²). A cylinder of 100 ft³ with a 2 ft radius is 100 ÷ 12.566 = 7.96 ft tall.
How many cubic inches are in a cubic foot?
Exactly 1,728, because a cubic foot is 12 in × 12 in × 12 in. Divide cubic inches by 1,728 to get cubic feet.
How do I convert cubic feet of a cylinder to cubic yards?
Divide by 27, since a cubic yard is 3 ft × 3 ft × 3 ft = 27 ft³. A cylinder of 169.65 ft³ is 6.283 yd³.
Related
- Cylinder volume in gallonsFind the volume of a cylinder in gallons: π × r² × h in inches ÷ 231, or in feet × 7.48052. US and imperial gallons, worked examples and a capacity chart.
- Concrete cylinderConcrete cylinder calculator for round columns, form tubes and post holes: volume in cubic feet and yards, bags of premix, waste margin and examples.
- Volume in litersCylinder volume in liters: π × r² × h in cm, divided by 1,000. Convert from mm, cm or m, with worked examples and a table of liters per cm for common diameters.
Updated October 12, 2026