How much concrete does a sonotube hold?

A round column holds π × radius² × height. A 12-inch tube (6-inch radius) standing 4 feet takes π × 0.5² × 4 ≈ 3.14 cubic feet, about 0.12 yd³ (0.089 m³). In metric, a 300 mm tube 1.2 m tall takes π × 0.15² × 1.2 ≈ 0.085 m³. Enter the tube diameter and height above and the volume, bag count and cubic-metre figure all update as you type.

Why is a round column less concrete than a square post?

Because a circle fits inside its bounding square with the corners left over — a circle fills about 78.5% of the square around it. A 12-inch round tube holds noticeably less than a 12-inch square form of the same height, which is why guessing from the box dimension over-orders every time.

How do I handle several piers at once?

Set the number of columns and the tool multiplies one tube by that count, assuming they are the same size. If your piers differ, run each size separately and add the results. The bag count and the ordered volume both reflect the total across every column.

Should I add waste for columns?

A little. Tube ends spill, the mix slumps as you rod it, and the very bottom of a bell or a footing pad under the tube swallows extra. Ten percent is a sensible start; on tall tubes filled from a barrow, nudge it up. It is the same reasoning as any pour — you cannot top up a column once it starts to set.

Concrete column calculator

Diámetro del tubo

Altura de la columna

Número de columnas

Factor de desperdicio

Derrames, asentamiento y la base bajo el tubo.

Rendimiento por saco

ft³/saco

Volumen mezclado por saco, según el saco — cámbielo por el suyo (0.6 ft³ es un saco de 80 lb; 0.014 m³, uno de 30 kg).

— yd³

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This multiplies the circle of your tube by its height and by the number of piers. It does not size the pier or its footing for the load above — take that from an engineered detail or your plans. Treat the volume as an ordering estimate and confirm it with your supplier.

Enter the tube's inside diameter and the height you are filling, set how many piers of that size you have, and the tool returns the concrete in cubic yards and cubic metres, plus a bag count. A column is a cylinder, so the volume is the area of the circle times the height.

Ejemplo resuelto

A 12-inch sonotube filled to 4 feet: the radius is 6 inches, or 0.5 ft, so one tube is π × 0.5² × 4 ≈ 3.14 cubic feet, which is 3.14 ÷ 27 ≈ 0.12 yd³. Six of them is about 18.8 cubic feet, or 0.70 yd³; add 10% and you would order around 0.77 yd³ (0.59 m³), roughly 35 bags at 0.6 ft³ each.

The same in metric: a 300 mm tube filled to 1.2 m has a 0.15 m radius, so one tube is π × 0.15² × 1.2 ≈ 0.085 m³. Six of them is 0.51 m³; add 10% and order about 0.56 m³ (0.73 yd³), or 40 bags at 0.014 m³ each.

En la obra

Deck piers, bagged. Eight 10 in tubes at 48 in: π × (5 ÷ 12)² × 4 = 2.18 ft³ each, 17.5 ft³ for the set, 19.2 with 10% — 32 bags at 0.6 ft³, or 0.71 yd³ if you priced a short load. Thirty-two bags is a morning with a mixer and a wheelbarrow; the truck's short-load fee usually loses at this size. The concrete page has the break-even comparer. In metric, eight 250 mm tubes at 1.2 m are 0.059 m³ each, 0.47 m³ for the set, 0.52 m³ with 10% — 38 bags at 0.014 m³.

The pad under the tube. If the detail puts a 24 in round footing 8 in thick under each pier, that is a second cylinder: π × 1² × 0.667 = 2.09 ft³ — nearly as much as the tube above it. Run the pads as their own set of columns (24 in diameter, 0.667 ft tall, eight of them) and add. Forgetting the pads is the usual way a pier pour comes up a dozen bags short. (Metric: a 600 mm pad 200 mm thick is π × 0.3² × 0.2 = 0.057 m³.)

Fence posts in a hole, not a tube. A 10 in auger hole 30 in deep is the same cylinder — 2.5 ft tall — less the post inside it (a 250 mm hole 750 mm deep is a 0.75 m column). The fence page works one through; put the hole in here as a column and knock the post volume off by hand.

What went wrong?

Quick referencefor round piers

ft³ per foot of tube: 8 in 0.35 · 10 in 0.55 · 12 in 0.79 · 14 in 1.07 · 16 in 1.40 · 18 in 1.77 · 24 in 3.14
Shortcut: ft³ per ft = 0.00545 × diameter² (diameter in inches)
Bags per 4 ft tube at 0.6 ft³, before waste: 8 in 2.3 · 10 in 3.6 · 12 in 5.2 · 16 in 9.3
The pad: a second, fatter cylinder under each tube — add it
Métrico: 250 mm: 0.049 m³ per m · 300 mm: 0.071 m³ per m · 30 kg bag ≈ 0.014 m³
Metric shortcut: m³ per m = 0.785 × diameter² (diameter in metres) · 1 m³ = 1.31 yd³

Waste & overagewhat to add, and why

Tube pours lose concrete to slump into a soft base and to the bell at the bottom if you bell the hole — 10% covers a tidy tube; 15–20% is honest for hand-dug holes. It goes in the waste field.
Buy bags in whole numbers per tube, not per job: six tubes at 3.6 bags each are 22 bags on the sum but six lots of 4 on the ground if you mix per hole.
One extra bag on the truck covers the tube that tears when the mix hits it.

Mistakes to catchbefore you order

Typing the tube diameter as the radius, or the radius as the diameter — the tool wants diameter; a 12 in tube typed as 6 gives a quarter of the concrete.
Measuring column height from grade instead of from the bottom of the hole to the top of the tube.
Leaving Number of columns at 1 for a deck with eight footings.

What an inspector looks forthe building inspector, before the piers are poured

On this part of the job

Diameter and depth of each hole, and the bell or pad at the bottom if the drawing shows one.
That the tube is plumb, braced, and sitting on bearing soil with no sloughed material in the bottom.
Vertical steel and ties where the detail calls for them — count, spacing, cover, and how far the bar projects out of the top for the connection above.
Anchor or saddle placement and height, and that they are held in position while the concrete is placed.
Distance to property lines and to any existing footing, because a pier is usually the piece of a deck or addition that ends up closest to a boundary.

Have this ready

The pier schedule from the drawing — diameter, depth and reinforcement for each one.
Hole covers or barricades; an open auger hole is its own safety item.
A tape long enough to read the full hole depth from grade.

Every figure an inspector measures against comes from the code your jurisdiction has adopted, the stamped drawing, or the manufacturer's printed instructions — so none of them are printed here. Look the number up in your own book, type it into the tool, and the arithmetic is yours.

La fórmula

volume = π × (diameter ÷ 2)² × height × columns

Diameter and height must share a unit before you multiply, so the tool drops the diameter into feet (or metres) first — inches ÷ 12, or millimetres ÷ 1000. The result is cubic feet, divided by 27 for cubic yards; in metric it is already cubic metres. Either way the other figure is shown too: 1 yd³ = 0.765 m³. Bags are the total volume over your per-bag yield.

What this tool assumes

Only that a full cylinder is π r² h and that 27 cubic feet make a yard — both definitions. The waste percentage and the bag yield are yours to set, because they are what genuinely varies from one job and one product to the next.

Preguntas

How much concrete does a sonotube hold?: A round column holds π × radius² × height. A 12-inch tube (6-inch radius) standing 4 feet takes π × 0.5² × 4 ≈ 3.14 cubic feet, about 0.12 yd³ (0.089 m³). In metric, a 300 mm tube 1.2 m tall takes π × 0.15² × 1.2 ≈ 0.085 m³. Enter the tube diameter and height above and the volume, bag count and cubic-metre figure all update as you type.
Why is a round column less concrete than a square post?: Because a circle fits inside its bounding square with the corners left over — a circle fills about 78.5% of the square around it. A 12-inch round tube holds noticeably less than a 12-inch square form of the same height, which is why guessing from the box dimension over-orders every time.
How do I handle several piers at once?: Set the number of columns and the tool multiplies one tube by that count, assuming they are the same size. If your piers differ, run each size separately and add the results. The bag count and the ordered volume both reflect the total across every column.
Should I add waste for columns?: A little. Tube ends spill, the mix slumps as you rod it, and the very bottom of a bell or a footing pad under the tube swallows extra. Ten percent is a sensible start; on tall tubes filled from a barrow, nudge it up. It is the same reasoning as any pour — you cannot top up a column once it starts to set.

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