Piers
Sonotube Concrete Calculator
A tube form is a solid cylinder. Pick 8, 10, 12, 16, 18, or 24 inches, then set the height and how many tubes you have.
Your region
Feet, inches, cubic yards, and 40–80 lb bags
Concrete Calculator
Example measurements — replace them with yours.
Common sizes
Most orders add 5–10% for spillage, uneven ground, and the last bit left in the chute.
Cost, truck size, and concrete weight
Leave a price blank to skip that estimate. Use the number your supplier quoted.
This job
Add each pour — slab, piers, steps — and Concrete Calculator totals them.
How to use a sonotube concrete calculator
A tube form is a solid cylinder. Concrete fills the tube — there is no hollow core to subtract. Sonotube is a common brand name; any round form with the same inside diameter holds the same concrete. “Sono tube” in search is the same pour.
Bells at the bottom are extra. Add them as a footing pour or measure the bell volume separately. Use the inside diameter that fills with concrete, not a printed outer wrap size if they differ.
Worked example: 12 in tube × 4 ft
π × 0.5² × 4 = 3.14 ft³. That is 6 bags of 80 lb mix before waste (3.14 ÷ 0.60). At 10% waste you still land on 6 bags until you clear 3.60 ft³. Four tubes stay a bag job; twenty start looking like a short truck.
An 18 in tube at 4 ft is 7.07 ft³ — more than double the 12 in tube at the same height, because area grows with the square of the radius. Re-run the Sonotube Concrete Calculator after thickness changes — depth moves yardage faster than length.
- 8 in → 0.349 ft³ per foot of height
- 10 in → 0.545 ft³/ft
- 12 in → 0.785 ft³/ft
- 16 in → 1.396 ft³/ft
- 18 in → 1.767 ft³/ft
- 24 in → 3.142 ft³/ft
Presets, quantity, and deck grids
Tap common diameters under Common sizes, then set height and quantity for a deck grid. Different corner heights need separate pours. Read the sonotube guide for per-foot bag counts you can check on site without opening a laptop.
Common mistakes
Subtracting a core that does not exist.
- Using the cardboard’s outer print size if it differs from the inside fill diameter.
- Ignoring the bell footing on a pier detail.
- Ordering one average height when corner posts are longer.
Bags, yards, or a truck?
Diameter grows volume with the square of the radius — jumping from 12 to 18 inches more than doubles concrete per foot. Fence posts in dug holes (not full tubes) belong on the post hole calculator.
The formula Concrete Calculator uses
ft³ = πr²h × quantity. Bags = ceil(ft³ ÷ yield).
Who this is for
Deck builders.
Fence and mailbox piers in cardboard forms.
8 and 12 sonotube concrete calculator presets
Eight-inch tubes are common for light posts; twelve-inch tubes show up under decks and small beams. Per-foot volumes: 0.349 ft³ (8 in) and 0.785 ft³ (12 in). Multiply by height and count. Bells and square caps are extra pours.
Sono tube calculator spelling redirects to the same math. Brand names vary; inside diameter rules the volume.
Related calculators and guides
Open the pages that match the next question on the job — volume is only the first number.
Frequently asked questions
How many bags for a 12 in sonotube?
About 0.785 ft³ per foot of height. A 4 ft tube ≈ 3.14 ft³ ≈ 6 bags of 80 lb.
How many yards in an 18 in tube?
1.767 ft³ per foot. A 10 ft pier ≈ 0.65 yd³.
Do I subtract the post?
Not in a full sonotube pier. For fence posts in dug holes, use the post hole calculator.
8, 10, 12 in presets?
Tap them under Common sizes, then set height and quantity.
Sono tube spelling?
Same calculator — diameter and height still drive the volume.