Concrete Estimator - Tube
Estimate the concrete volume needed to fill sonotube, fiber, or cardboard cylindrical forms — mix multiple tube sizes in one job.
Tube Forms (mix different sizes in one job)
Add one row per tube diameter you're pouring — a job with a mix of 8 in, 12 in, and 16 in sonotubes can all be estimated together, with the total volume, bags, and cost combined automatically.
Concrete Volume by Tube Size (cubic yards)
This chart breaks down the concrete volume for each tube size you entered, plus the final total after adding your waste allowance.
Tube Form Diagram
Side-view diagram of your first tube entry, to scale, with diameter and height labeled.
Step-by-Step Solution
Here's exactly how this answer was calculated, one step at a time.
- 1
Tube 1: volume of one tube × quantity
Volume = π × (1 ÷ 2)² × 4 ft = 3.142 ft³ per tube × 6 tubes = 18.85 ft³
A cylindrical tube form is solved with the cylinder volume formula, π × radius² × height, then multiplied by how many identical tubes of that size you're pouring.
- 2
Add up every tube size
Tubes Total = 18.8 = 18.85 ft³
Every row's volume is summed together, so you can mix different diameters and heights in one estimate.
- 3
Add a 5% waste allowance
Total Volume = 18.85 × (1 + 5/100) = 19.79 ft³ (0.733 yd³)
A waste allowance covers spillage, tube form seepage, and minor over-excavation at the base.
✓ Final Answer: you need about 0.733 cubic yards of concrete
Free Online Concrete Estimator - Tube
This concrete estimator - tube works out exactly how much concrete you need to fill sonotube, fiber, or cardboard cylindrical forms, whether you're pouring a single deck footing or a whole job site full of piers in different sizes. Just enter each tube's diameter, height, and how many identical tubes you're pouring, and the calculator instantly shows the total volume in cubic yards, the number of bags if you're mixing by hand, and the material cost.
Unlike a basic single-tube calculator, this tool lets you mix and match multiple tube diameters in one estimate — a genuinely common situation on real job sites, where a deck might use 8 inch tubes for railing posts and 12 inch tubes for the main structural footings, all poured in the same day.
What Are Concrete Tube Forms?
A concrete tube form — often sold under the brand name Sonotube, though fiber and cardboard tubes from other manufacturers work the same way — is a round, waxed cardboard or fiber cylinder used to shape a column of poured concrete below or above grade. They're the standard way to form deck footings, fence post footings, bollards, and small structural piers, since a round tube is quick to set, level, and backfill compared to building square plywood formwork for the same job.
Tube forms come in a wide range of standard diameters, typically from about 6 inches up to 36 inches or more, and can be cut to any height on site with a handsaw, which is exactly why a flexible, multi-size calculator like this one is more useful than a single fixed-size tool.
Concrete Tube Volume Formula
Here's the formula this calculator uses for every tube you enter, then sums together:
- Single Tube Volume = π × (Diameter ÷ 2)² × Height
- Row Volume = Single Tube Volume × Quantity
- Tubes Total = Sum of every row's volume
- Flare Footing Volume (optional) = π × (Flare Diameter ÷ 2)² × Flare Height, added per tube
- Total Volume = (Tubes Total + Flare Footings) × (1 + Waste Allowance %)
Why Tube Diameter Matters More Than People Expect
Because the cylinder volume formula squares the radius, a fairly small increase in tube diameter produces a much bigger jump in concrete volume than most people expect. Going from an 8 inch tube to a 12 inch tube — only 4 inches wider — more than doubles the volume needed for the same height, since the cross-sectional area scales with the square of the radius, not the diameter itself.
This is exactly why mixing up tube sizes on a quick mental estimate leads to real shortfalls on pour day. Entering each tube size as its own row in this calculator, rather than averaging sizes together, keeps the total accurate even on a job with several different tube diameters.
How to Use This Concrete Tube Estimator
Start by entering the diameter and height of your first tube size, along with how many identical tubes of that size you're pouring. If your job uses more than one tube diameter — for example, wider footings at the corners and narrower ones along the run — click "Add another tube size" to add as many rows as you need, each with its own diameter, height, and quantity.
If your footings widen out into a flared, bell-shaped base for extra bearing capacity in soft soil, check "Include Flared Footing at Base" and enter the flare's diameter and height — this calculator approximates that flare as a short, wide cylinder added underneath every tube, which is accurate enough for material estimating even though the real shape is usually a tapered cone or dome.
Add a waste allowance to cover spillage, tube form seepage at the base, and minor over-excavation — 5% is a reasonable default for a straightforward tube pour. Finally, choose whether you're ordering ready-mix concrete by the cubic yard or mixing bagged premix on site, and enter your local pricing if you want a cost estimate for the whole job.
Worked Example
Say you're pouring six 12 inch diameter tubes, each 4 feet tall, for a deck's main footings, plus four 8 inch diameter tubes, each 3 feet tall, for the railing posts. The 12 inch tubes have a diameter of 1 foot, so each one is π × 0.5² × 4 = 3.14 cubic feet, and six of them come to 18.85 cubic feet. The 8 inch tubes have a diameter of 0.667 feet, so each one is π × 0.333² × 3 = 1.05 cubic feet, and four of them come to 4.19 cubic feet.
Adding both rows together gives a tubes total of about 23 cubic feet. With a 5% waste allowance, that comes to roughly 24.2 cubic feet, or about 0.9 cubic yards of ready-mix concrete — small enough that many contractors would just order a short-load delivery or mix it by hand with around 41 bags of 60 lb premix.
Common Uses for Tube Form Concrete Estimates
Tube form concrete calculations come up across a wide range of residential and light commercial projects:
- Deck builders use it to size footings for support posts, factoring in local frost-depth requirements for footing height.
- Fence contractors use it for gate post and line post footings, especially on longer runs with dozens of identical holes.
- Homeowners and DIY builders use it for mailbox posts, pergola footings, and small shed piers.
- Landscapers use it to plan bollard covers and decorative post bases poured in cylindrical forms.
- Contractors bidding multi-size jobs use the multi-row feature to combine every tube size on a job into a single, accurate material order.
Common Mistakes When Estimating Tube Concrete
A few errors come up again and again when people estimate tube volume by hand:
- Using the diameter directly in the volume formula instead of dividing it in half to get the radius first, which overstates the volume by a factor of 4.
- Averaging several different tube diameters together into one "typical" size instead of calculating each size separately, which skews the total in either direction.
- Forgetting to account for a flared footing at the base, which is common on footings designed for soft or frost-prone soil.
- Mixing diameter and height units (for example, entering diameter in inches and height in meters) without converting them first.
- Skipping a waste allowance, which matters more than people expect on tube pours since some concrete is always lost to seepage through the cardboard tube wall before it's fully cured.
Advanced Features in This Calculator
This tool goes beyond a basic single-cylinder calculator with a few features built for real job-site takeoffs:
- Multi-row support for mixing different tube diameters, heights, and quantities in a single combined estimate — add up to eight tube sizes at once.
- An optional flared footing add-on, approximating the extra bell-shaped base many deck and post footings use for added bearing capacity in soft soil.
- Independent unit selection for diameter, height, and the flare footing, so you can mix inches, feet, and meters freely across a single job.
- A live breakdown chart showing the volume contributed by each individual tube size, so you can see exactly where the concrete is going before ordering.
- Support for both ready-mix and bagged concrete ordering, with automatic bag-size yield conversion and a total material cost estimate.
Frequently Asked Questions
How much concrete do I need for a sonotube?
Use the cylinder volume formula: π × radius² × height, where the radius is half the tube's diameter. For example, a 12 inch (1 foot) diameter tube that's 4 feet tall needs about 3.14 cubic feet of concrete. This calculator applies that formula automatically and lets you combine several different tube sizes into one total.
How many bags of concrete do I need for a tube form?
It depends on the tube's volume and the bag size. An 80 lb premixed bag yields about 0.6 cubic feet, a 60 lb bag yields about 0.45 cubic feet, and a 40 lb bag yields about 0.3 cubic feet. Divide your total tube volume in cubic feet by the bag's yield to get the number of bags needed — this calculator does that conversion automatically for whichever bag size you choose.
Can I estimate multiple different tube sizes at once?
Yes. This calculator lets you add up to eight separate tube entries, each with its own diameter, height, and quantity, and combines them into one total volume, bag count, and cost — useful for jobs that mix, say, 8 inch and 12 inch tubes on the same site.
What is a flared footing and do I need one?
A flared (or bell-shaped) footing widens out at the bottom of a tube form to spread the load over a larger area of soil, which is often required by code for deeper footings or softer soil conditions. Check your local building code or an engineer's drawing to see if your footings need one, then use the optional flare footing feature to add that volume to your estimate.
Why does tube diameter affect concrete volume so much?
Cylinder volume depends on the radius squared, so even a modest increase in diameter produces a much larger jump in volume. Going from an 8 inch to a 12 inch tube more than doubles the concrete needed for the same height, which is why it's important to calculate each tube size separately rather than estimating with an average diameter.
Should I add extra concrete for waste on a tube pour?
Yes, a waste allowance of around 5% is a reasonable default, covering spillage, minor seepage through the tube wall, and slight over-excavation at the base. Taller or narrower tubes, or jobs with many individual pours, may benefit from a slightly higher allowance.
What's the difference between this and a sonotube-specific calculator?
The underlying cylinder volume math is the same for any round tube form regardless of brand — Sonotube is simply the most common brand name for these fiber concrete forms. This calculator is built to handle a full job with multiple tube sizes and an optional flared footing in one pass, rather than solving for just a single tube at a time.