Concrete Column Calculator
Filling a round column, pier, or tube form? Enter the diameter and height to get the concrete you need in cubic yards and in 40, 60, and 80-lb bags. Set a quantity for several.
Free · no sign-up ·
You need · incl. +10% extra
- 40-lb bags
- 12
- Cubic feet
- 3.5 ft³
- Cubic meters
- 0.1 m³
- Exact volume
- 0.12 yd³
Use cubic yards to order ready-mix by the truck; bag counts for a smaller hand-mixed pour. Bag yields: 80-lb ≈ 0.6 ft³, 60-lb ≈ 0.45 ft³, 40-lb ≈ 0.3 ft³.
Order about 10% extra — you can’t pause a pour to mix more, and the subgrade is never perfectly level. Past ~½ yard, ready-mix is usually cheaper and far less work than bags.
The formula
Volume = π × (diameter ÷ 2)² × height (× quantity). Convert to cubic yards (1 yd³ = 27 ft³). Bags = volume in ft³ ÷ bag yield (80-lb ≈ 0.6 ft³).
How to estimate concrete for a concrete column
A round concrete column — a pier, a deck footing, or a fence-post core formed with a cardboard tube like a Sonotube — is sized by the area of its circle times its height. The area is π times the radius squared, and the radius is half the diameter, so a 12-inch tube has a 6-inch (0.5-foot) radius and holds about 0.79 cubic feet per foot of height. The calculator does the circle math for you from the diameter.
Columns add up faster than people expect. A single 12-inch pier 4 feet tall is only about 3.1 cubic feet — well within bag territory (about 6 eighty-pound bags). But a row of them, or a wider tube, climbs quickly: set the quantity to the number of identical columns and the calculator totals them. Past roughly half a cubic yard total, ready-mix starts to make sense.
Order about 10% extra, and remember the tube must be plumb and braced before you pour — concrete is heavy and will push an unbraced form out of line. For the gravel under a pier or the bedding around a post, the Gravel and Sand calculators size those.
Frequently asked questions
How much concrete do I need for a column?+
Volume = π × (radius)² × height. For a 12-inch-diameter tube (6-inch radius) 4 feet tall, that is about 3.1 cubic feet, or 0.12 cubic yards — roughly 6 eighty-pound bags with waste. Enter the diameter and height above for an exact figure.
How many bags of concrete for a Sonotube?+
A 12-inch tube holds about 0.79 cubic feet per foot of height, so a 4-foot column (≈3.1 ft³) takes about 6 eighty-pound bags with waste. Wider tubes need far more — the calculator handles any diameter and height.
How much concrete per foot of tube?+
About 0.20 cubic feet per foot for an 8-inch tube, 0.44 for a 10-inch, 0.79 for a 12-inch, and 1.23 for a 16-inch tube. Multiply by the height for the total, or let the calculator do it.
How do I calculate concrete for several columns?+
Enter the diameter and height of one column and set the quantity to the number of identical columns. The calculator multiplies the volume and totals the bags and cubic yards.
How deep should a column or pier footing be?+
Below the frost line in cold climates — often 36–48 inches — and bearing on firm soil. The required depth is set by your local code and the load, so confirm before you dig.
What size Sonotube do I need?+
Common sizes are 8, 10, 12, and 16 inches in diameter; the right one depends on the load (a deck post versus a structural pier). The calculator works for any diameter you enter — set it to your tube size.
Should I use bags or ready-mix for columns?+
Bags are usually fine for a few columns — a handful of piers is well under a cubic yard. For many columns or large-diameter tubes that total more than about half a yard, ready-mix is cheaper and easier.
How much extra concrete should I order for columns?+
About 10%. Tubes are rarely cut to an exact height and some concrete is lost to spillage and the form, so order a little over. The calculator includes an adjustable overage.
Do I need to brace a concrete tube before pouring?+
Yes — the tube must be plumb and braced before the pour, because wet concrete is heavy and will push an unbraced form out of alignment. The calculator estimates quantity, not formwork.
Is this concrete column calculator free?+
Yes — free, no sign-up, and it runs entirely in your browser, so nothing you enter is stored or sent anywhere.