Cubic Yards In A Cylinder Calculator

Find the volume of a cylinder in cubic yards from its diameter and height using V = π × r² × h, useful for concrete footings, columns, tube forms, and round tanks.

Quick Facts

Formula
V = π × r² × h, then ÷ 27 for cubic yards
r is the radius — half the diameter, not the diameter itself.
Conversion
1 cubic yard = 27 cubic feet
Ready-mix concrete is commonly ordered in cubic yards, often rounded up to the nearest 1/4 yard.

Your Results

Calculated
Volume per cylinder
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Cubic feet (ft³)
Volume per cylinder
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Cubic yards (yd³)
Total volume
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Cubic yards for the full quantity, exact
Recommended order
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Cubic yards, with waste allowance, rounded up

Ready

Enter the diameter and height, then press Calculate.

Formula and method for cubic yards in a cylinder

A cylinder's volume is V = π × r² × h, where r is the radius (half the diameter) and h is the height or depth. That formula gives cubic feet when r and h are in feet. Because ready-mix concrete, fill dirt, and gravel are almost always priced and delivered in cubic yards, the last step divides by 27 — the number of cubic feet in one cubic yard (3 ft × 3 ft × 3 ft).

How the calculation works

This calculator takes a diameter in inches and a height in feet — the common way post holes, tube forms (like Sonotube), and round columns are specified — and converts everything to feet before applying the formula. Diameter is converted to radius (diameter ÷ 2), then radius is converted from inches to feet (÷ 12) before squaring. The volume per cylinder in cubic feet is π × r² × h; dividing by 27 converts that to cubic yards. Multiplying by the quantity gives the exact total for every cylinder you enter. A separate waste-allowance percentage — commonly 5–10% in concrete work to cover spillage, uneven excavation, and minor form irregularities — is then added, and the result is rounded up to the nearest quarter cubic yard, a typical ready-mix ordering increment, to give a practical order quantity.

Common mistakes

  • Diameter vs. radius: the formula needs the radius, not the diameter. Using diameter directly in r² quadruples the volume instead of dividing it correctly — this calculator handles that conversion for you.
  • Mixed units: keep diameter, height, and any other measurement in a consistent system. This tool assumes diameter in inches and height in feet; convert first if your measurements use different units.
  • Forgetting the 27: cubic feet and cubic yards are frequently confused. One cubic yard equals 27 cubic feet, not 3 — because the conversion is cubed (3³ = 27), not linear.

Real-world applications

  • Concrete footings, fence-post holes, and round piers sized from a hole diameter and depth
  • Sonotube or other cylindrical form pours for columns and deck footings
  • Round water tanks, silos, or cisterns where capacity is needed in cubic yards
  • Ordering fill, gravel, or topsoil for a cylindrical planter, well, or excavation

Frequently Asked Questions

What is the formula for cubic yards in a cylinder?
Volume = π × r² × h, where r is the radius (half the diameter) and h is the height, both in feet. This gives cubic feet; divide by 27 to convert to cubic yards, since one cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft).
Do I enter diameter or radius?
Enter the diameter — the full width across the circle — in inches. The calculator divides it by 2 to get the radius and by 12 to convert inches to feet before applying V = π × r² × h. Entering the radius where diameter is expected would understate the volume by roughly a factor of four.
Why does the calculator add a waste allowance?
The geometric volume (V = π × r² × h ÷ 27) is the exact mathematical amount of material the cylinder holds. In practice, concrete and fill orders commonly include a 5–10% waste allowance to account for spillage, uneven excavation, and form irregularities, and are rounded up to the nearest 1/4 cubic yard because that is a typical ready-mix ordering increment. Set the waste allowance to 0% to see the exact geometric volume instead.
How many cubic yards are in a typical post hole?
A 12-inch-diameter hole that is 4 feet deep has a radius of 0.5 feet, giving V = π × 0.5² × 4 ≈ 3.14 cubic feet, or about 0.116 cubic yards — roughly 1/9 of a cubic yard. Multiply by the number of holes for a total, then add a waste allowance before ordering.

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