How Much Concrete Do You Need for Sonotubes?

A single 12-inch sonotube at 48 inches deep holds about 3.14 cubic feet of concrete before waste. Four of those tubes need roughly 13.82 cubic feet (0.51 cubic yards) with a 10% waste buffer, which works out to 24 bags of 80 lb mix or 31 bags of 60 lb mix. The exact amount depends on tube diameter, depth, and how many footings your project requires. Use the sonotube calculator to get bag counts and cubic yards for your specific setup.

How cylindrical volume determines your concrete order

Sonotubes are cylinders, so the volume formula is different from the rectangular slab math most people know. Instead of length times width times depth, you calculate:

Volume per tube (cubic feet) = π × Radius² × Depth (ft)

Radius is half the tube diameter. Because sonotubes are sold by inside diameter in inches, you need to convert both the diameter and the depth to feet before plugging numbers in.

For a 12-inch tube: divide 12 by 12 to get 1 foot, then divide by 2. Radius = 0.5 feet. For a 48-inch depth: divide 48 by 12. Depth = 4 feet.

Plug those in: π × 0.5² × 4 = π × 0.25 × 4 = 3.14 cubic feet per tube.

That per-tube number is the building block for your entire concrete order. Get it right and the rest of the math is just multiplication.

From one tube to a total project volume

Most projects have more than one footing. A simple backyard deck might need 4 tubes. A large wraparound deck or pergola could call for 8 to 12.

The difference between a single-tube volume and your full project total is straightforward: multiply the per-tube cubic feet by the number of tubes, then divide by 27 to convert to cubic yards. Suppliers sell ready-mix by the cubic yard, so that conversion matters when you’re comparing bagged mix to a truck delivery.

Total volume (cubic feet) = Volume per tube × Number of tubes

Cubic yards = Total volume / 27

For four 12-inch tubes at 48 inches deep: 3.14 × 4 = 12.57 cubic feet, or about 0.47 cubic yards before waste.

Always add a waste factor. Concrete spills around the tube base, overfills uneven cuts, and seeps into loose soil at the bottom of the hole. A 10% buffer is standard for DIY pours. With waste, that 12.57 becomes 13.82 cubic feet (0.51 cubic yards).

This is where people run into trouble. They calculate one tube perfectly, skip the waste multiplier, and end up short on material halfway through the pour. Wet concrete does not wait while you drive to the store for three more bags.

Converting cubic feet to bag counts

Most homeowners buy concrete in bags, not by the yard. Bag yield determines how many you need to load into the truck:

Bag size	Yield per bag	Bags for 13.82 cu ft
60 lb	0.45 cu ft	31 bags
80 lb	0.60 cu ft	24 bags

To calculate bag count, divide total cubic feet (with waste included) by the yield per bag and round up. You can’t buy a partial bag, so always round to the next whole number.

80 lb bags = Total cu ft / 0.60 (rounded up)

60 lb bags = Total cu ft / 0.45 (rounded up)

The 80 lb bags give you more concrete per dollar and fewer bags to open. But each one weighs 80 pounds, and hand-mixing 20+ bags in a wheelbarrow is genuinely exhausting work. The 60 lb bags are easier to lift and mix, which makes them a better choice if you’re working alone or have a back that complains.

For larger pours (roughly 30+ bags), many crews switch to ready-mix delivery at $170 to $220 per cubic yard in 2026. You lose flexibility on timing, but you save hours of mixing labor and get a more consistent result.

Worked example: common sonotube sizes at 48 inches deep

The table below shows concrete needs for the most popular tube diameters, all at a standard 48-inch depth with 10% waste applied. Compare your tube size to find a quick ballpark before running exact numbers through the sonotube calculator.

Tube diameter	Volume per tube	4-tube total (with waste)	80 lb bags	60 lb bags
8 in	1.40 cu ft	6.16 cu ft	11 bags	14 bags
10 in	2.18 cu ft	9.59 cu ft	16 bags	22 bags
12 in	3.14 cu ft	13.82 cu ft	24 bags	31 bags
16 in	5.58 cu ft	24.55 cu ft	41 bags	55 bags
18 in	7.07 cu ft	31.11 cu ft	52 bags	70 bags

Notice the jump from 12-inch to 16-inch tubes. Volume nearly doubles because you’re squaring the radius in the formula. Moving up one tube size has a bigger impact on concrete needs than most people expect. Always check the actual diameter printed on the tube packaging rather than measuring with a tape, since tubes can compress slightly during shipping.

An 8-inch tube at 4 feet deep only needs 11 bags of 80 lb mix for a 4-footing project. Bump that to 18-inch tubes and the same 4 footings require 52 bags. That’s the difference between a quick Saturday morning pour and a full-day job with a helper.

Real-world tips that save trips to the store

Buy more bags than the math says. On a recent 6-footing deck project with 12-inch tubes, the calculated amount was 36 bags of 80 lb mix. The holes on one side of the yard were 3 inches deeper than expected because the ground slopes, and the pour used 39 bags. That 10% waste factor exists for exactly this kind of surprise.

Check your local frost line depth. In cold-climate US areas, building codes typically require footings 36 to 48 inches below grade. A footing that stops at 30 inches can fail inspection even if it looks solid. Your local building department publishes the exact frost depth for your county, and it directly changes how much concrete you need per tube.

Hand-mixing gets brutal past 20 bags. Four 12-inch sonotubes need about 24 bags of 80 lb mix. That’s 1,920 pounds of concrete you’re lifting, dumping into a wheelbarrow, adding water to, mixing, and shoveling into tubes. For 8 or more tubes, price out a half-yard ready-mix delivery. The per-yard cost is higher, but you save hours of labor and get a stronger, more consistent pour.

Cut tubes before the pour, not during. Mark your tube height with a level and cut with a reciprocating saw while the tube is still dry and empty. Trimming a sonotube full of wet concrete is messy, inaccurate, and changes your fill volume.

Vibrate or rod the concrete after pouring. Push a piece of rebar or a stick up and down through the wet mix a few times to release air pockets. Trapped air weakens the footing and wastes some of the volume you paid for.

When to use the sonotube calculator

Counting bags by hand works fine for one or two tubes, but the math gets tedious when you’re pricing a full deck with 6 to 12 footings in mixed sizes. The sonotube calculator handles diameter, depth, quantity, and an adjustable waste percentage in one step. It returns cubic feet, cubic yards, both 60 lb and 80 lb bag counts, and estimated cost ranges so you can compare bagged mix against ready-mix delivery before you order.

If your footings also need vertical reinforcement, the rebar calculator estimates bar lengths and total steel weight for rebar inside the tube.