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Tube & Post Hole Concrete Calculation
Calculate concrete for Sonotube · Concrete Piers · Post Hole / Fence Posts
Units & Grade
Select Shape / Type
🔵 Hollow tube — wall thickness required for accurate volume
Dimensions
ft
ft
ft
Number of Units
How many sonotubes?
1
Total = single × qty
Wastage Buffer
Accounts for spillage, overpouring & formwork loss 7%
⚠️ Please enter valid positive values in all required fields.
✅ Calculation complete — 1 Sonotube · M20
Total Net Volume
—
m³
Order Volume (incl. wastage)
—
m³
Approx. Weight
—
tonnes
Premix Bags (50 kg)
—
× 50 kg bags
MaterialMix RatioQuantity Required

Sonotube Concrete Calculator

Pouring a sonotube without the right estimate means running back to the store mid-job. Use our free sonotube concrete calculator to get exact volume, cubic feet, and bag counts for any tube diameter and depth. Works for deck piers, fence posts, and structural columns with fast and accurate.

Three Tools. Every Pour Type Covered.

Concrete Tube Calculator​

Enter your sonotube diameter and depth and get cubic feet, cubic yards, and exact bag count for 40 lb, 50 lb, 60 lb, and 80 lb bags instantly. Works as a full concrete tube calculator for any round cardboard form available in the USA and Australia. Best for deck piers, pergola posts, mailbox bases, and structural footings.

Concrete Pier Calculator

Our concrete pier calculator is built for deeper load bearing piers. Handles standard and bell-bottom pier designs. Use it as a concrete hole calculator for large-diameter structural applications. Best for deck framing, heavy gate posts, and timber frame column bases where depth and diameter both vary.

Concrete Post Hole Calculator

Handles fence post layouts with multiple holes. Enter hole diameter, depth, and total post count and get a full material estimate across the entire job. Works as a concrete calculator for fence posts and post holes in one input. Best for privacy fences, chain-link installs, and split-rail fence lines.

Frequently Asked Questions

How many bags of concrete for a 12-inch sonotube at 4 feet deep?

A 12-inch tube at 4 feet deep holds approximately 3.77 cubic feet. That’s about 6 bags of 80 lb mix or 8 bags of 60 lb mix. For Sakrete or Quikrete 50 lb bags, plan on 10 bags. Always buy one extra to avoid a mid-pour shortage.

At 2 feet deep, an 8-inch sonotube needs roughly 1 bag of 80 lb mix. At 3 feet deep, use 2 bags of 80 lb or 3 bags of 50 lb. Enter your exact depth into our concrete tube calculator for a precise result.

At 3 feet deep, a 10-inch sonotube needs about 3 bags of 80 lb mix. At 4 feet deep, budget 4 bags of 80 lb or 6 bags of 50 lb. Depth matters more than diameter here in always calculate before you buy.

Sakrete 80 lb bags yield 0.60 cubic feet each. A 12-inch sonotube at 3 feet deep needs about 5 bags. At 4 feet deep, plan on 6 to 7 bags. Our sonotube concrete calculator works with any brand, just enter your tube dimensions and select your bag size.

Use the formula: π × r² × depth = cubic feet. Then divide by your bag yield. For an 80 lb bag, divide by 0.60. For a 50 lb bag, divide by 0.375. Or skip the math entirely and enter your diameter and depth into our concrete pier calculator above and get instant results.

In the USA, sonotube piers must extend below the local frost line. That ranges from 12 inches in the Deep South to 48 inches or more in northern states like Minnesota, Wisconsin, and Maine. For deck piers, most local building codes require a minimum of 12 inches of bearing into undisturbed soil below the frost line. Always check your local frost depth map before you pour.

 Yes, Quikrete 5000, Fast-Setting Concrete, and standard 80 lb bags all work well in sonotube forms. Quikrete 5000 reaches 5,000 PSI strength and is a popular choice for structural deck piers. Just make sure your mix is wet enough to fully consolidate inside the tube, rod or vibrate it to eliminate air pockets.

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