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Concrete Column Calculator

Enter the column shape, size, height, and quantity to estimate the concrete needed.

How it is calculated

For a round column V = π × (d ÷ 2)² × h; for a square column V = s² × h. In both cases the single size field (dim) is the diameter or the side length, and the height and dim are in metres. The volume per column is multiplied by the count. The tool then converts: cubic yards = m³ ÷ 0.764555, and bags = ceil(m³ × 35.3146667 ÷ 0.45), assuming one 60-lb bag yields 0.45 cubic feet. Any shape value other than square is treated as round, so a rectangular column cannot be entered; for it, multiply width × depth × height yourself. No waste, spillage or over-excavation allowance is added, and every value must be above zero. Bag yields vary by brand and country, so check the label.

Worked example

Six round columns, each 0.4 m in diameter and 3 m tall. Radius = 0.2 m. One column: π × 0.2² × 3 = 0.377 m³. Six columns: 0.377 × 6 = 2.262 m³. In cubic yards: 2.262 ÷ 0.764555 = 2.959 yd³. In cubic feet: 2.262 × 35.3147 = 79.9 ft³, and 79.9 ÷ 0.45 = 177.5, rounded up to 178 bags.

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Common mistakes

  • Typing the diameter in centimetres (40) or the height in feet; both are metres, so 0.4 is a 40 cm column.
  • Entering the radius as the size for a round column. The field expects the diameter; using 0.2 gives one quarter of the real volume.
  • Using the "square" option for a rectangular column or leaving the shape on round for it. Only square and round are supported, and anything else is read as round.
  • Ordering exactly the calculated amount. Add an allowance for spillage, uneven formwork and a reserve at the pour; the figure here is the theoretical volume.
  • Relying on the bag count for a big pour; around 178 bags of 60 lb is heavy work, and the ready-mix volume is the figure to order from.

About this calculator

Pouring a concrete column means knowing exactly how much ready-mix concrete to order or how many bags to buy, and that comes down to a simple volume formula applied to the column's cross-section. For a round column, volume = π × radius² × height; for a square (or rectangular) column, volume = width × depth × height — multiplied by however many identical columns you're pouring.

The calculator converts that raw volume into the units contractors actually order in: cubic meters or cubic yards for ready-mix trucks, and the number of 60-lb bags (each yielding about 0.45 cubic feet of mixed concrete) for smaller jobs done by hand.

Contractors, DIY builders, and estimators use this before a pour to avoid the two costly mistakes of ordering concrete: running short mid-pour (creating a weak cold joint) or paying for truck minimums on far more than needed.

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Comments (1)

  • Editorial team

    The shape choice changes the order noticeably when the same size number is used. A column with a 0.4 m size and 3 m height needs 0.377 m³ as a round column but 0.480 m³ as a square one, so check which formwork you are really building. Cardboard tube forms and timber boxes also differ in how well they hold the figure. For rectangular sections you must compute the volume by hand. What column sections are you pouring?

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