Concrete Cylinder Volume Calculator - Columns & Pillars

A concrete cylinder volume calculator finds how much concrete a cylindrical shape needs, such as a column, pillar, or post footing. It uses the diameter and height of the cylinder to give the volume in cubic meters.

Concrete cylinder volume formula

A cylinder's volume equals pi times the radius squared, times the height:

$V = \pi \times r^2 \times h$

• V is the volume, in cubic units.
• π (pi) is a constant, about 3.14159.
• r is the radius, in linear units.
• h is the height, in linear units.

Most people measure the diameter, not the radius, so the radius is found first:

$r = \frac{d}{2}$

Combining the two gives a formula that starts from diameter directly:

$V = \pi \times \frac{d^2}{4} \times h$

Diameter and height must be entered in the same unit. This calculator works in meters and gives volume in cubic meters (m³).

How to calculate concrete cylinder volume

1. Measure the diameter of the cylinder in meters. If the form is not perfectly round, measure it in two directions at right angles and average the results.
2. Measure the height in meters. On sloped ground, measure at a few points and average them.
3. Divide the diameter by 2 to get the radius.
4. Square the radius (multiply it by itself).
5. Multiply by pi (about 3.14159).
6. Multiply by the height. The result is the volume in cubic meters.

Worked example

A column has a diameter of 0.5 m and a height of 3 m.

1. Radius = 0.5 ÷ 2 = 0.25 m
2. Radius squared = 0.25² = 0.0625
3. 0.0625 × π ≈ 0.19635
4. 0.19635 × 3 ≈ 0.589 m³

The column needs about 0.589 m³ of concrete. Because real pours rarely match a calculation exactly, most builders order 5–10% more. At 10% extra, that is 0.589 × 1.10 ≈ 0.65 m³ to order.

Converting the result to other units

• 1 m³ = 1.31 cubic yards (yd³)
• 1 m³ = 35.31 cubic feet (ft³)
• 1 m³ = 1,000 liters (L)

A common error is measuring diameter in centimeters but forgetting to convert it to meters. Mixing units this way can throw the volume off by a factor of 100.

Estimating bags of concrete

Bag yield varies by product, but a rough rule of thumb is that a 25 kg bag of dry ready-mix concrete produces about 0.01 m³ once mixed. Divide the volume by 0.01 to estimate the number of bags. The table below uses this rule; check the yield printed on the bag being used, since it can differ.

Common uses for cylindrical concrete

Round columns and posts spread load evenly around their surface, without the sharp corners that concentrate stress in square columns. That makes the cylinder a common shape in construction.

• Structural columns. A column 600 mm across and 3 m tall needs about 0.85 m³ of concrete.
• Fence post footings. A hole 300 mm across and 600 mm deep needs about 0.04 m³, roughly four 25 kg bags.
• Garden planters and bollards. A planter 500 mm across and 600 mm tall needs about 0.12 m³, roughly twelve 25 kg bags.
• Foundation piles and bridge piers, which can run 10–20 m deep and use much larger volumes.

These figures assume a solid cylinder. Hollow shapes, such as pipes, need a different calculation, covered below.

Hollow cylinders

This calculator finds the volume of a solid cylinder. A hollow cylinder, such as a concrete pipe or a planter with walls, needs a different formula: the outer cylinder's volume minus the inner cavity's volume.

$V = \pi \times h \times (R^2 - r^2)$

Here R is the outer radius and r is the inner (cavity) radius.

Example: a pipe with a 1.0 m outer diameter, a 0.8 m inner diameter, and a 2 m height.

• Outer volume: π × 0.5² × 2 ≈ 1.571 m³
• Inner volume: π × 0.4² × 2 ≈ 1.005 m³
• Concrete needed: 1.571 − 1.005 ≈ 0.566 m³

Why order extra concrete

Contractors commonly order 5–10% more concrete than the calculated volume. A few things cause the actual amount needed to run higher than the theoretical figure:

• Spills during pouring
• Wooden forms bulging outward under pressure
• An uneven subgrade under the pour
• Air pockets removed by vibrating the wet concrete, which slightly reduces its volume and can require topping up
• Small measurement errors in diameter or height

A 10% buffer is typical for structural work like columns. A 5% buffer is often enough for smaller, non-structural jobs like fence posts.

Frequently asked questions

How do I convert a concrete volume to weight? Multiply the volume in m³ by the concrete's density. Standard concrete density is about 2,300–2,400 kg/m³. One cubic meter at 2,350 kg/m³ weighs 2,350 kg.

How many bags of concrete do I need? Divide the volume in m³ by the yield of one bag. Using the common estimate of 0.01 m³ per 25 kg bag, a job needing 0.2 m³ takes about 20 bags. Check the actual yield printed on the bag, since it varies by brand.

Does this calculator work for hollow cylinders, like pipes? No. It calculates a solid cylinder. For a hollow cylinder, find the outer cylinder's volume, find the inner cavity's volume, and subtract one from the other, as shown above.

Does steel reinforcement (rebar) change the volume needed? Rebar usually displaces less than 3% of a column's volume. That is small enough to fall within a normal 5–10% waste buffer, so it can usually be ignored.

How do I calculate concrete for several identical cylinders? Calculate the volume of one cylinder, then multiply by the number of cylinders needed. For cylinders of different sizes, calculate each separately and add the results.

What if the cylinder sits on sloped ground? Measure the height at several points around the cylinder and use the average as the height in the formula.