Sonotube Calculator
Find the concrete needed to fill cylindrical forming tubes (Sonotube) for piers, columns, and footings. Enter the tube diameter, height, and how many tubes, add a little waste, and get the volume in cubic yards and cubic feet, the number of 40 / 60 / 80 lb bags, and the ready-mix and bag cost — with by-diameter and by-bag-size tables and a downloadable PDF.
| Diameter | Per tube | Cubic yards | Bags |
|---|---|---|---|
| Enter a tube to compare sizes | |||
| Bag | Yield | Bags | Cost |
|---|---|---|---|
| Enter a tube to compare bags | |||
How to use the Sonotube calculator
Enter the tube diameter, the pour height and how many tubes, add a waste allowance, and get the concrete in cubic yards and cubic feet, the number of 40 / 60 / 80 lb bags and the ready-mix and bag cost — with by-diameter and by-bag-size tables and a downloadable PDF.
Set diameter & count
Pick a standard tube size or type a custom diameter, then how many identical tubes you’re pouring.
Enter the pour height
The full height of each tube in feet or inches, including the part below grade for footings.
Add waste & bag size
A waste allowance (10% is common) and your pre-mix bag size, plus optional prices.
Read the result & save a PDF
See cubic yards, bags and cost, compare diameters and bag sizes, and download it for the yard.
How the concrete estimate is calculated
A Sonotube is just a cylinder, so the volume is the circle’s area times the height. From there it’s bags, yards and cost — with a waste allowance on top before anything is rounded up.
Worked example — four 8″ tubes, 4 ft tall, 80 lb bags, 10% waste
Per tube: π ÷ 4 × (8 ÷ 12)² × 4 = 1.40 ft³
Four tubes: 1.40 × 4 = 5.59 ft³
With 10% waste: 5.59 × 1.10 = 6.15 ft³
Cubic yards: 6.15 ÷ 27 = 0.23 yd³
Bags: 6.15 ÷ 0.60 = 10.25 → 11 bags
Four 8-inch piers 4 feet deep need about 0.23 cubic yards of concrete — roughly eleven 80-lb bags once waste and rounding are in.
Sonotube concrete reference charts
The numbers that come up most — concrete per foot by tube size, how much a full pour needs, and how many bags fill a cubic yard.
| Diameter | Per foot | Per 4 ft | 80-lb bags / ft |
|---|---|---|---|
| 6 in | 0.20 ft³ | 0.79 ft³ | 0.3 |
| 8 in | 0.35 ft³ | 1.40 ft³ | 0.6 |
| 10 in | 0.55 ft³ | 2.18 ft³ | 0.9 |
| 12 in | 0.79 ft³ | 3.14 ft³ | 1.3 |
| 16 in | 1.40 ft³ | 5.59 ft³ | 2.3 |
| 18 in | 1.77 ft³ | 7.07 ft³ | 2.9 |
Volume climbs with the square of the diameter — an 18-inch tube holds about nine times the concrete of a 6-inch one at the same height. Bag counts here are before waste and rounding.
| Diameter | Total volume | Cubic yards | 80-lb bags |
|---|---|---|---|
| 6 in | 3.5 ft³ | 0.13 yd³ | 6 |
| 8 in | 6.2 ft³ | 0.23 yd³ | 11 |
| 10 in | 9.6 ft³ | 0.36 yd³ | 16 |
| 12 in | 13.8 ft³ | 0.51 yd³ | 23 |
| 16 in | 24.6 ft³ | 0.91 yd³ | 41 |
Values rounded. Notice how quickly four 16-inch tubes approach a full cubic yard — around there, ready-mix usually beats bags on cost and effort.
| Bag size | Yield | Bags per cu yd |
|---|---|---|
| 40 lb | ~0.30 ft³ | 90 bags |
| 60 lb | ~0.45 ft³ | 60 bags |
| 80 lb | ~0.60 ft³ | 45 bags |
Yields are typical for standard pre-mix and vary a little by brand. Once you’re near a full yard — about forty-five 80-lb bags — ready-mix delivery is usually the cheaper, faster call.
The concrete for a Sonotube pour comes from three inputs: the diameter and the height set the volume of one tube, and the number of tubes multiplies it. Add waste, and that’s the concrete — yards, bags and weight.
- Diameter dominates — volume grows with the square of the diameter, so size moves the total fast.
- Height and count are linear — twice the depth or twice the tubes is simply twice the concrete.
- Waste then rounding — add waste on top, then round up to whole bags or a yard figure to order.
Everything the calculator works out
One set of inputs gives you the volume in cubic yards and cubic feet, the bag count, the concrete weight and the cost — plus a comparison across diameters and bag sizes, and a report for the yard.
The figures behind every pour
Built for anyone pouring piers, columns or footings
A deck, a fence, a pergola, a set of structural columns — the volume math is the same, and knowing the yards and bags before you dig means one concrete order and no half-set pour waiting on a store run.
Pouring a handful of deck or fence footings and wanting the exact bag count so one trip covers the job.
- Set height to full pour depth
- Add 10% waste
- Buy whole bags, a little extra
Spec’ing concrete across many tubes and deciding where bags give way to ready-mix by the yard.
- Compare bags vs cubic yards
- Price both for the quote
- Save the PDF to the job
Sizing footing pours to depth and code, weighing tube diameter against total concrete and cost.
- Match depth to the frost line
- Check volume by diameter
- Confirm footing size with code
7 tips for Sonotube pours
The things that quietly blow a concrete order or a footing — and the checks that get the pour right the first time.
Sonotube concrete FAQ
The volume, bag and footing questions people ask most when pouring piers, columns and footings in forming tubes.
The volume of one tube is π ÷ 4 × diameter² × height, all in feet. Work in feet from the start, then divide by 27 for cubic yards.
An 8-inch tube 4 feet tall holds about 1.4 cubic feet, or 0.05 cubic yards; four of them come to about 5.6 cubic feet before waste. The calculator does this for any diameter, height and tube count, and adds your waste allowance.
Divide the total volume by the bag’s yield and round up. Typical yields are about 0.60 cubic feet for an 80-lb bag, 0.45 for a 60-lb bag and 0.30 for a 40-lb bag.
An 8-inch tube 4 feet tall is about 1.4 cubic feet, so roughly three 80-lb bags per tube. Because you always round up to whole bags, buy a little extra — and for several tubes the count adds up fast, which is where ready-mix often wins.
Bags make sense for a few small piers where mixing by hand or in a small mixer is manageable. Past roughly a cubic yard — very roughly forty-five 80-lb bags — ready-mix delivered by the truck is usually cheaper and far less work.
Count your total cubic yards first. A handful of 8-inch tubes may be a bag job; a row of 12-inch columns several feet deep quickly crosses into ready-mix territory. The calculator shows both the bag count and the cubic yards so you can compare.
Deep enough to reach below the local frost line and bear on stable soil — the depth is set by your climate and building code, not by the tube. Frost depth ranges from almost nothing in warm regions to four feet or more in cold ones.
Set the calculator’s height to your full pour depth, including the part below grade. Always confirm the required footing depth, diameter and any bell or spread base with your local code and, where needed, an engineer.
It depends on the load and what the column or pier supports — common sizes run from 6 and 8 inches for light duty up to 12, 16 and 18 inches for heavier posts and columns. Bigger diameters carry more but use dramatically more concrete.
Because volume grows with the square of the diameter, a 12-inch tube holds more than twice the concrete of an 8-inch one at the same height. The by-diameter table lets you see that jump before you choose, but the structural size should come from the design or an engineer.
Because concrete volume depends on the diameter squared. Doubling the diameter quadruples the cross-section area, so it quadruples the concrete for the same height — a 16-inch tube holds four times what an 8-inch tube does.
That’s why a small bump in tube size can turn a bag job into a ready-mix order. The calculator’s by-diameter chart and table show the climb clearly, so you can weigh size against concrete cost before committing.
Around 10 percent is a common allowance for Sonotube pours. It covers spillage, slightly oversize holes, over-dig at the base, and the concrete that spreads out below the tube if the bottom isn’t formed.
Add more if your holes are rough, the base flares out, or you’re pumping. It’s better to have a little extra than to stop a pour short, so the calculator applies your waste percent on top of the raw volume and then rounds the bags up.
Concrete weighs about 150 pounds per cubic foot, or roughly 4,050 pounds — just over two tons — per cubic yard. So even a modest set of piers adds up to a serious load on your forms, bracing and the ground below.
An 8-inch tube 4 feet tall holds about 1.4 cubic feet, around 210 pounds of concrete. The calculator reports the total weight so you can plan bracing, access and how much you can safely mix and place at once.
Estimate Only — Not an Engineered Footing Design: This calculator finds concrete volume from the cylinder formula — volume per tube = π ÷ 4 × diameter² × height — and converts to bags using typical yields (80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 40 lb ≈ 0.30 ft³), with concrete at about 150 lb/ft³. Actual yield varies by product and mix, so add waste for spillage and over-dig and round up. It does not determine footing diameter, depth, reinforcement or bearing capacity — those depend on the load, soil, frost line and local building code. For reference and estimating only; confirm footing size, depth and design with your local code and a qualified engineer where required.