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Concrete Tube Calculator

Home & ConstructionConcrete and Masonry
Measure in
Concrete needed (cubic yards) —
Total cubic feet
—
Total cubic metres
—
One tube, no waste (ft³)
—
80 lb bags
—
60 lb bags
—

A round form tube holds π × radius² × height of concrete. An 8 inch tube poured 4 feet deep has a radius of 1/3 ft, so it holds 3.1416 × 0.111 × 4 = 1.40 cubic feet, about 0.05 cubic yards. That takes three 80 lb bags or four 60 lb bags before any waste allowance.

About this tool

Deck builders, fence installers and anyone setting post or column footings in cardboard form tubes need to know how much concrete each pier swallows before ordering. Enter the tube diameter, how deep the pour goes and how many tubes you are filling, then set a waste allowance for spillage and the flared hole bottom. The calculator returns the total in cubic yards, cubic feet and cubic metres, the volume of a single tube, and how many 60 lb or 80 lb premix bags cover the job, with the working shown line by line. It assumes a straight cylinder; a bell or spread footing at the base adds volume the tube formula does not include, so estimate that part separately.

How to use it

  1. Pick your units

    Choose inches and feet or centimetres and metres; the size fields switch to match.

  2. Enter tube size

    Type the inside diameter of the form and the full height of concrete, including any part above grade.

  3. Set the count

    Use the − and + buttons to set how many identical tubes you are pouring.

  4. Adjust waste

    Slide the waste allowance; 5–10% covers spillage and an over-dug hole bottom.

Examples

One 8 in deck footing, 4 ft deep

Measure in
Inches and feet
Tube diameter
8
Pour height
4
Number of tubes
1
Waste allowance
0

Result Concrete needed (cubic yards): 0.05
Total cubic feet: 1.4
Total cubic metres: 0.04
One tube, no waste (ft³): 1.4
80 lb bags: 3
60 lb bags: 4

  1. Radius = 0.6667 ft ÷ 2 = 0.3333 ft
  2. One tube = π × 0.3333² × 4 ft = 1.396 ft³
  3. 1.396 ft³ × 1 tubes = 1.396 ft³
  4. With 0% waste: 1.396 ft³ = 0.052 yd³ = 0.04 m³
  5. 80 lb bags: 1.396 ÷ 0.60 → 3; 60 lb bags: ÷ 0.45 → 4

A typical deck pier below the frost line holds about 1.4 cubic feet, which three 80 lb bags cover.

Ten 12 in piers, 4 ft each

Measure in
Inches and feet
Tube diameter
12
Pour height
4
Number of tubes
10
Waste allowance
0

Result Concrete needed (cubic yards): 1.16
Total cubic feet: 31.42
Total cubic metres: 0.89
One tube, no waste (ft³): 3.14
80 lb bags: 53
60 lb bags: 70

  1. Radius = 1 ft ÷ 2 = 0.5 ft
  2. One tube = π × 0.5² × 4 ft = 3.142 ft³
  3. 3.142 ft³ × 10 tubes = 31.416 ft³
  4. With 0% waste: 31.416 ft³ = 1.164 yd³ = 0.89 m³
  5. 80 lb bags: 31.416 ÷ 0.60 → 53; 60 lb bags: ÷ 0.45 → 70

Ten piers need 31.4 cubic feet, just over a cubic yard, so a ready-mix order starts to make sense.

30 cm tube, 1.2 m tall

Measure in
Centimetres and metres
Tube diameter
30
Pour height
1.2
Number of tubes
1
Waste allowance
0

Result Concrete needed (cubic yards): 0.11
Total cubic feet: 3
Total cubic metres: 0.085
One tube, no waste (ft³): 3
80 lb bags: 5
60 lb bags: 7

  1. Radius = 0.9843 ft ÷ 2 = 0.4921 ft
  2. One tube = π × 0.4921² × 3.937 ft = 2.995 ft³
  3. 2.995 ft³ × 1 tubes = 2.995 ft³
  4. With 0% waste: 2.995 ft³ = 0.111 yd³ = 0.085 m³
  5. 80 lb bags: 2.995 ÷ 0.60 → 5; 60 lb bags: ÷ 0.45 → 7

A metric pier of 30 cm by 1.2 m takes about 0.085 cubic metres of concrete.

How it is calculated

V = π × (d ÷ 2)² × h × n × (1 + w ÷ 100)

d
tube inside diameter, in feet
h
height of the concrete column, in feet
n
number of tubes
w
waste allowance, percent

Each tube is treated as a right cylinder. Metric inputs are converted to feet first (30.48 cm and 0.3048 m per foot). Cubic feet divide by 27 for cubic yards and multiply by 0.0283168 for cubic metres. Bag counts divide the total by Quikrete's published yields, 0.60 ft³ per 80 lb bag and 0.45 ft³ per 60 lb bag, and round up to whole bags.

When not to use it

  • Square or rectangular columns need a length × width × height calculation instead.
  • Footings with a plastic bell base need the bell volume added on top of this figure.
  • Structural piers sized by an engineer should follow the volumes on the drawings.

Common mistakes

  • Measuring the hole depth but forgetting the tube section that sticks up above grade.
  • Entering the outside diameter of a thick-walled form instead of its inside diameter.
  • Buying exactly the computed bag count with no allowance for a wider hole bottom.
  • Mixing up 60 lb and 80 lb bag yields when pricing the job.

Frequently asked questions

How many bags of concrete fill a 12 inch tube 4 feet deep?

A 12 inch tube 4 feet tall holds π × 0.5² × 4 = 3.14 cubic feet. At 0.60 cubic feet per 80 lb bag that is 6 bags, or 7 bags of the 60 lb size, before waste.

How much concrete does a 6 inch tube need per foot?

A 6 inch tube has a radius of 0.25 ft, so each foot of height holds π × 0.0625 = 0.196 cubic feet. A 4 foot pier therefore takes about 0.79 cubic feet, a little over one 80 lb bag.

What waste allowance makes sense for form tubes?

Most installers add 5 to 10 percent. Augered holes are rarely perfectly sized, the bottom is often wider than the tube, and some mix is lost when filling. Hand-dug holes with a flared base can need more.

When is ready-mix better than bags?

Around one cubic yard, about 45 bags of 80 lb mix, the labour of hand mixing usually outweighs the delivery charge. Many suppliers have a short-load fee below that, so compare both prices for jobs near the threshold.

Does the part of the tube below ground count?

Yes. Enter the full height of the concrete column from the bottom of the hole to the top of the tube, because the whole length is filled with concrete.

Can I use this for metric tube sizes?

Switch the units to centimetres and metres. A 30 cm tube poured 1.2 m tall holds about 0.085 cubic metres; the bag counts still use the US 60 lb and 80 lb yields.