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Sonotube Cylindrical Pier Concrete Calculator

Calculate exact concrete volume and bag requirements (80-lb and 60-lb) for round cardboard Sonotubes, cylindrical deck piers, fence post footings, and pole barn foundations. Includes individual pier breakdowns and total ready-mix yardage.

Measurements

US customary
in
ft
piers
Tube Diameter (in) Pier Depth (ft)
Cylindrical cast-in-place pier • ACI 318 frost depth standard
ESTIMATE READY
Total Concrete Volume
1.31 yd³
For 6 piers: order 1.31 cubic yards ready-mix or 59 eighty-pound bags.
80-lb pre-mix bags (0.60 cu ft yield) 59 Bags
60-lb pre-mix bags (0.45 cu ft yield) 79 Bags
Total placed cubic feet 35.2 cu ft
Volume per single pier 5.86 cu ft
80-lb bags per single pier 10 Bags
Field Guide & Technical Contents

How to Calculate Cylindrical Concrete Pier Volume Manually

Sonotubes and round concrete pier forms are geometric cylinders. To calculate the volume, determine the cross-sectional circle area using the radius, multiply by the depth, multiply by the number of posts, and convert cubic feet into cubic yards or commercial bag equivalents.

The Cylindrical Pier Formula:
Radius (ft) = Diameter (in) ÷ 24
Cubic Feet = pi × (Diameter ÷ 24)² × Depth (ft) × Quantity × (1 + Waste)
Cubic Yards = Total Cubic Feet ÷ 27 quad Big| quad 80-lb Bags = ⌈ Total Cubic Feet ÷ 0.60 ⌉

Worked-Out Jobsite Numerical Example

Suppose you are pouring foundations for an elevated outdoor deck requiring 6 cylindrical piers. Each pier is 12 inches in diameter and 4 feet deep (extending beneath a 36-inch regional frost line), with a 10% overage allowance.

  1. Calculate Radius in Feet: 12 inches / 24 = 0.5 ft.
  2. Calculate Single Pier Cross-Section Area: pi × r² = 3.14159 × (0.5)² = 0.7854 sq ft.
  3. Calculate Single Pier Volume: 0.7854 sq ft × 4.0 ft (depth) = 3.1416 cu ft.
  4. Calculate Total Volume for 6 Piers: 3.1416 cu ft × 6 = 18.85 cu ft.
  5. Apply 10% Waste Buffer: 18.85 × 1.10 = 20.73 total cu ft.
  6. Convert to Cubic Yards: 20.73 / 27 = 0.77 cubic yards.
  7. Determine Bag Count:
    • 80-lb Bags: 20.73 / 0.60 = 34.6 rightarrow 35 Bags.
    • 60-lb Bags: 20.73 / 0.45 = 46.1 rightarrow 47 Bags.

Technical Reference: Sonotube Diameter & Bag Yield Chart

This reference schedule compares standard cardboard tube diameters, cubic foot displacement per linear foot of depth, and 80-lb concrete bag counts for common residential pier depths:

Tube Diameter (Inches) Volume per 1 Ft Depth 80-lb Bags per 1 Ft Depth Volume for 4 Ft Frost Pier 80-lb Bags for 4 Ft Pier (with 10% waste)
8-Inch Tube 0.35 cu ft 0.58 Bags 1.40 cu ft (0.05 yd³) 3 Bags
10-Inch Tube 0.55 cu ft 0.91 Bags 2.18 cu ft (0.08 yd³) 4 Bags
12-Inch Tube 0.79 cu ft 1.31 Bags 3.14 cu ft (0.12 yd³) 6 Bags
14-Inch Tube 1.07 cu ft 1.78 Bags 4.28 cu ft (0.16 yd³) 8 Bags
16-Inch Tube 1.40 cu ft 2.33 Bags 5.59 cu ft (0.21 yd³) 11 Bags
18-Inch Tube 1.77 cu ft 2.95 Bags 7.07 cu ft (0.26 yd³) 13 Bags
24-Inch Tube 3.14 cu ft 5.24 Bags 12.57 cu ft (0.47 yd³) 23 Bags
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\n Looking for pier footing standards, rebar cages & frost line depths?\n

For complete ACI cylindrical foundation standards, starter dowel lap charts, and frost-heave mitigation, review our in-depth Concrete Estimating & Pouring Guide →

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Frequently Asked Questions About Sonotube Calculation

A 12-inch sonotube requires 1.32 eighty-pound (80 lb) bags of concrete per foot of depth. For a standard 4-foot deep frost-line deck footing, you will need 5.3 bags (order 6 bags per pier).
Calculate sonotube concrete volume in cubic yards using the formula: (3.1416 * (Diameter in inches / 24)^2 * Depth in feet) / 27. Multiply by the total number of piers to get the complete project yardage.
A 12″ diameter by 4-foot deep tube has a net volume of 3.14 cubic feet. Factoring in a 10% waste buffer (3.45 cu ft), you need 6 bags of 80-lb pre-mix concrete per pier.
Fast-setting concrete (such as red-bag Quikrete) is formulated for fence posts where you pour dry mix into a hole and add water. Do not use dry fast-setting mix in Sonotubes deeper than 2 feet. Water cannot penetrate evenly through a 4-foot deep cardboard column, leaving pockets of unhydrated, powdery dry cement in the bottom that cause structural collapse. Always pre-mix concrete with water before placing it into deep tubes.
When pouring concrete into a cardboard tube, wet concrete creates buoyant hydraulic upward pressure. Backfill soil around the outside of the tube up to ground level and tamp firmly before pouring, or screw 2×4 wooden cleats across the top of the tube staked into the ground.
Most municipal residential building codes (IRC) require a minimum compressive strength of 2,500 to 3,000 PSI at 28 days for exterior footings. Standard yellow-bag commercial concrete mix achieves 3,500 to 4,000 PSI, which exceeds code requirements and provides superior durability against freeze-thaw cycles.
Planning Disclaimer

Results are estimates based on the dimensions and material assumptions entered. Actual material requirements can vary due to site conditions, material density, compaction, waste, supplier specifications, and construction methods. Confirm quantities with your supplier or project professional before ordering.

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