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Concrete, Masonry & Stone

Concrete Cylinder Calculator

Concrete for round footings, piers, sonotubes and column bases, by diameter and depth.

Your measurements

Enter one cylinder; the count multiplies the result.

Cylinder
Piers of different sizes should be run separately and added.
Mix and waste
Tube ends, spillage and slightly oversized holes. Hand dug holes need more than augered ones.

Your result

Sample values

1.15

Cubic yards

31.1

Cubic feet

52

80 lb bags

3.46

Cubic feet each

Nine 12 in piers at 4 ft deep, 10% waste.

What to order

Sold as Quantity
80 lb bags 52 bags
60 lb bags 70 bags
Ready mix 1.25 yd³ ordered
Pallets of 80 lb bags (42) 2 pallets

How to use this calculator

Measure the diameter of the hole or tube and the depth you are filling, then enter how many identical cylinders you are pouring. If your piers vary, run each size separately rather than averaging — the volume goes up with the square of the diameter, so averaging under-orders badly.

Where a pier has a flared or belled base, work out the bell separately and add it. The calculator treats every cylinder as a straight tube.

Formula

Volume = π × Radius² × Depth

Radius = Diameter ÷ 2

Total = Volume × Count × (1 + Waste)

π
approximately 3.1416
Radius
converted to feet before squaring

Doubling the diameter quadruples the concrete; depth only scales it linearly.

Worked example

Nine deck piers, 12 in sonotubes, 4 ft deep, 10% waste, 80 lb bags.

  1. 12 in diameter ÷ 2 = 6 in radius, or 0.5 ft
  2. π × 0.5² = 0.785 ft² of cross section
  3. 0.785 ft² × 4 ft = 3.14 ft³ per pier
  4. 3.14 ft³ × 9 piers = 28.3 ft³
  5. 28.3 ft³ × 1.10 = 31.1 ft³ with waste
  6. 31.1 ft³ ÷ 0.60 ft³ per bag = 52 bags

31.1 cubic feet, or 52 bags of 80 lb mix

Understanding your results

Bag counts climb fast on round pours. Fifty-two bags is roughly a ton and a half of material to carry, mix and place, which is the point at which most people start pricing a ready mix delivery instead. Suppliers usually have a minimum load and a short load fee, so compare the delivered price against the bag price including your own time.

The cubic yard figure is what a ready mix plant works in. Order to the next quarter yard rather than the exact number — running out mid pier means a cold joint in a structural element, which is a much worse outcome than a little leftover.

Questions

About this calculator

Ask something else

Below the frost line for your area, which ranges from nothing in the far south to five feet or more in northern states. Your local building department publishes the depth and it is not negotiable — a pier that sits above the frost line will lift and drop with the seasons and take the deck with it.

Fill to the finished height you want the pier to reach, which is usually a few inches above grade so water drains away from the post base. Cut the tube to that height before pouring rather than pouring short and trying to judge it from above.

For anything carrying structural load, yes — vertical bars tied to the post anchor keep the pier acting as one piece if the ground moves. Requirements vary by jurisdiction and by what the pier supports, so check the code rather than guessing.

Because the hole is rarely as tidy as the tube. Cardboard forms bulge slightly when filled, hand dug holes are wider than nominal at the bottom, and some mix is always left in the barrow. Ten percent is a reasonable allowance for formed piers and low for unformed holes.

Keep going

All Concrete, Masonry & Stone tools
Estimates, not specifications. Results are based on the values you enter and on typical material properties. Densities, coverage rates and product sizes vary between suppliers, so confirm quantities against your supplier's data before ordering. Structural work must be signed off by a qualified professional and meet your local building code.