Concrete Column Fill Calculator
Estimate the concrete needed to fill a round column in cubic yards. Enter the diameter in inches and the height in feet — useful for piers, form tubes and structural columns.
Estimate Concrete for Round Column Fill
Concrete Column Fill Formula
Where:
- \(d\) — diameter of the column, in inches
- \(r\) — radius of the column, in feet (dividing the diameter by 24 converts inches to feet and halves it)
- \(h\) — height (depth) of the column, in feet
- \(\frac{22}{7}\) — approximation of \(\pi\)
- \(27\) — number of cubic feet in one cubic yard
This is the standard cylinder volume formula \(V = \pi r^{2} h\), with the diameter converted from inches to a radius in feet and the answer converted from cubic feet to cubic yards.
Concrete Column Fill – Calculation Example
Example: a round form tube 12 inches in diameter and 4 feet tall must be filled with concrete. Enter Height / Depth = 4 and Diameter = 12.
\[ r = \frac{12}{24} = 0.5 \text{ ft} \]
\[ V = \frac{4 \times 0.5^{2} \times \frac{22}{7}}{27} = \frac{3.1429}{27} \approx 0.1164 \text{ yd}^{3} \]
Result: about 0.12 cubic yards of concrete for one column.
How to Use the Calculator
- Measure the height (or depth) of the column in feet and enter it in the Height / Depth field.
- Measure the inside diameter of the column or form tube in inches and enter it in the Diameter field.
- Read the result in the Cubic yards field — this is the concrete needed to fill one column.
- For several identical columns, multiply the result by the number of columns and add a 5–10% waste margin before ordering.
What Is Concrete Column Fill?
Round concrete columns appear in many projects: deck piers, porch columns, pole-barn posts, sign footings and the cylindrical piers that support beams under a house. The concrete is usually poured into cardboard form tubes (often called Sonotubes) or into hollow steel columns, and the amount needed depends on only two dimensions — the diameter and the height of the cylinder.
Ready-mix concrete is sold by the cubic yard, so estimating the volume in cubic yards lines up directly with how you order it. A single small column is often below a supplier's minimum load — commonly around one cubic yard — in which case bagged concrete mix is more practical. An 80 lb bag yields roughly 0.6 ft³ (about 0.022 yd³) of concrete, so the 12 in × 4 ft column in the example above needs a little over five bags; round up to six to allow for waste.
The result is the net volume of the cavity. To turn it into an order, multiply by the number of columns, add the waste margin, and compare with delivery sizes. If you are pouring footings or a slab at the same time, add this result to the estimate from our concrete footing and slab pours calculator so the whole job is covered by a single delivery. To check the total for the entire project, the concrete yardage calculator is also handy.
Concrete Needed per Foot of Column Height
The table below shows the fill volume of a round column per foot of height, using the same formula as the calculator. Multiply the value by the column height in feet.
| Diameter (in) | Concrete per foot of height (yd³) | Concrete per 10 ft column (yd³) |
|---|---|---|
| 8 | 0.0129 | 0.13 |
| 10 | 0.0202 | 0.20 |
| 12 | 0.0291 | 0.29 |
| 16 | 0.0518 | 0.52 |
| 18 | 0.0655 | 0.65 |
| 24 | 0.1164 | 1.16 |
| 30 | 0.1819 | 1.82 |
| 36 | 0.2619 | 2.62 |
Assumptions, Limitations and Tips
- Height in feet, diameter in inches. The calculator converts the diameter to a radius in feet (\(d \div 24\)) but uses the height value exactly as entered, so enter the height in feet for a correct cubic-yard result. If your height is measured in inches, divide it by 12 before entering it.
- Straight, vertical cylinder. The formula assumes a uniform diameter over the full height. Tapered columns or piers with a belled, wider base need the extra footing volume computed separately — see the concrete footing yardage calculator.
- Rebar and inserts. Reinforcing bars, anchor bolts and inner posts displace a small amount of concrete, typically 1–3% — usually covered by the waste margin.
- Approximate π. The calculator uses 22/7 for \(\pi\), which differs from the true value by less than 0.04% — negligible for ordering purposes.
- Order extra. Add 5–10% for spillage, an uneven excavation bottom and variations in mixing; a ready-mix supplier generally cannot deliver a small top-up load.
- Round columns only. For rectangular columns or walls, use the concrete wall calculator instead.
Frequently Asked Questions
How do I calculate the concrete for a round column by hand?
Use the cylinder formula \(V = \pi r^{2} h\). Divide the diameter in inches by 24 to get the radius in feet, square it, multiply by the height in feet and by \(\pi\) — the result is cubic feet. Then divide by 27 to convert to cubic yards. For a 10-inch tube 5 feet tall: \(r = 10/24 \approx 0.417\) ft, \(V \approx 0.417^{2} \times 5 \times \pi \div 27 \approx 0.10\) yd³.
Should I enter the height above ground or the full tube length?
Enter the full length of concrete you will pour — including the portion below ground. Deck piers and footings often extend below the frost line, and that buried section still needs concrete. If part of the hole will be filled with gravel for drainage, measure only the depth that will actually be concrete, not the total hole depth.
How do I convert the result into bags of concrete mix?
Multiply the cubic yards by 27 to get cubic feet, then divide by the yield per bag. An 80 lb bag yields about 0.6 ft³, and a 60 lb bag about 0.45 ft³. So 0.12 yd³ (3.14 ft³) needs roughly six 80 lb bags. Always round up and buy one or two extra bags — running short mid-pour is a bigger problem than leftovers.
Why is my result wrong when I enter the height in inches?
The formula assumes the height is in feet; only the diameter is converted automatically. If you enter 48 instead of 4 for a 4-foot column, the answer is 12 times too large. Divide any height measured in inches by 12 first, or express it in decimal feet (e.g., 4 ft 6 in = 4.5 ft). This is the most common mistake with this type of calculation.
How much concrete do I need for a common Sonotube size?
Per foot of height: a 10-inch tube takes about 0.02 yd³, a 12-inch tube about 0.03 yd³, and an 18-inch tube about 0.07 yd³. So a 12-inch tube sunk 4 feet deep needs roughly 0.12 yd³, or about six 80 lb bags. Since even several columns rarely reach a supplier's one-yard minimum load, bagged mix is usually the cheaper choice for small jobs.
Do I subtract the volume of the rebar cage or a wood post inside the tube?
Rebar cages and anchor bolts displace very little — typically 1–3% of the volume — which the usual 5–10% waste margin already covers. A solid wood or steel post set in the concrete displaces more: subtract its cross-sectional area times the embedded depth. For a 6×6 post in a 12-inch tube, that removes about 20% of the concrete needed.
What if my pier has a flared or belled bottom?
The calculator only handles a straight cylinder of uniform diameter. A belled base, a wider pad, or a stepped footing must be estimated separately — treat the bell as a short, wider cylinder or a frustum and add its volume to the column result. Compare the combined total with your supplier's minimum load before deciding between ready-mix and bagged concrete.