Sonotube Concrete Bag Calculator

Calculate exactly how many bags of concrete you need for your sonotube footings.

Building a deck? Installing fence posts? Pouring footings for a new structure? If you’ve got sonotubes waiting to be filled, the burning question is always the same: “How many bags of concrete do I actually need?”

Buy too few, and you’re making an emergency hardware store run with wet concrete setting up. Buy too many, and you’ve got expensive bags collecting dust in your garage for years.

This calculator takes the guesswork out of concrete planning. Enter your dimensions, select your bag size, and get a complete materials list in seconds.

Sonotube Concrete Bag Calculator | Free Footing Estimator

📐 Sonotube Dimensions

Common Tube Diameters (click to select)

Tube Diameter

inches

Inner diameter of sonotube

Tube Depth/Height

inches

Total depth below + above ground

Number of Tubes

tubes

How many identical footings?

Concrete Bag Size Select bag size you’ll use

Total Bags Needed

80 lb bags

For 4 tubes × 12″ diameter × 48″ deep

📦

Bags Per Tube

bags each

📐

Volume Per Tube

3.14

cubic feet

🧊

Total Volume

12.57

cubic feet

⚖️

Total Weight

1,920

pounds

💧

Water Needed

gallons (approx)

📊

Cubic Yards

0.47

cu yd

📋 Calculation Breakdown

Tube Diameter: 12 inches

Tube Depth: 48 inches (4 ft)

Number of Tubes: 4 tubes

Volume Formula: π × r² × h

Bag Yield: 0.60 cu ft/bag

Waste Factor: +10% included

💰 Estimated Cost Range

Budget Estimate

$120

@ $5.00/bag

Average Estimate

$156

@ $6.50/bag

Premium Estimate

$192

@ $8.00/bag

✅

Recommendation

For this project, bagged concrete is ideal. The quantity is manageable and you’ll have good control over the pour.

📊 Visual Representation

📖 How to Use This Calculator

Select Diameter

Choose your sonotube size or enter custom diameter

Enter Depth

Input total tube height/depth in inches

Set Quantity

Enter how many identical tubes you need to fill

Get Results

View bags needed, volume, weight & cost estimate

📊 Quick Reference: Bags Needed by Tube Size

Diameter	Volume/Foot	2 ft Deep	3 ft Deep	4 ft Deep	5 ft Deep
6″	0.20 cu ft	1 bag	1 bag	2 bags	2 bags
8″	0.35 cu ft	2 bags	2 bags	3 bags	4 bags
10″	0.55 cu ft	2 bags	3 bags	4 bags	5 bags
12″	0.79 cu ft	3 bags	4 bags	6 bags	8 bags
14″	1.07 cu ft	4 bags	6 bags	8 bags	10 bags
16″	1.40 cu ft	5 bags	8 bags	10 bags	13 bags
18″	1.77 cu ft	7 bags	10 bags	13 bags	17 bags
24″	3.14 cu ft	12 bags	17 bags	23 bags	29 bags

* Based on 80 lb bags (0.60 cu ft yield) with 10% waste factor

💡 Pro Tips for Sonotube Projects

🎯 Buy Extra

Always purchase 10-15% more bags than calculated. Waste, spillage, and slightly oversized holes are common. Unused bags can usually be returned.

💧 Water Matters

Use exactly the recommended water amount. Too much water weakens concrete; too little makes it unworkable. Aim for a thick, oatmeal-like consistency.

⏱️ Time It Right

Standard concrete gives you 1-2 hours of working time. Fast-setting concrete sets in 20-40 minutes. Plan your pours accordingly.

🔩 Set Hardware First

Install post anchors, J-bolts, or brackets while concrete is wet. Don’t wait until it sets — repositioning cured concrete is impossible.

📏 Check Frost Line

Footings must extend below your local frost line to prevent heaving. This ranges from 12″ (warm climates) to 48″+ (cold regions).

🏗️ Brace Tubes

Secure sonotubes with stakes and bracing before pouring. Wet concrete is heavy and will shift unsupported tubes.

📦 Bag Size Comparison

40 lb: Easiest to handle, ideal for small projects or limited mobility. Lower cost per bag but less yield.

60 lb: Good balance of handling and efficiency. Common at many retailers.

80 lb: Most economical per cubic foot. Best for larger projects. Can be heavy for some users.

🚛 When to Order Ready-Mix

Consider ready-mix concrete delivery when your project exceeds 1 cubic yard (27 cu ft). Benefits include:

Consistent mix quality
Significant time savings
Often more economical for large pours
Less physical labor

⏰ Curing Times

Walk-on ready: 24-48 hours

Post mounting: 24-48 hours for light loads

50% strength: 7 days

Full strength: 28 days

Keep concrete moist during first week for best results.

❓ Frequently Asked Questions

How do I calculate concrete for a sonotube?

Use the cylinder volume formula: Volume = π × (diameter/2)² × height. Convert to cubic feet, then divide by your bag’s yield (0.60 cu ft for 80 lb bags). Our calculator does this automatically and adds a 10% waste factor.

How many 80 lb bags fill a 12″ sonotube?

For a 12″ diameter sonotube, you need approximately 1.5 bags per linear foot of depth. A standard 4-foot deep tube requires about 6 bags of 80 lb concrete, including waste allowance.

Should I use 60 lb or 80 lb bags?

80 lb bags are more economical and efficient for larger projects. 60 lb bags are easier to handle and better for smaller jobs or users with physical limitations. The concrete quality is identical regardless of bag size.

How much water do I add per bag?

For 80 lb bags, add approximately 3 quarts (0.75 gallons). For 60 lb bags, use about 2.25 quarts. Start with less water and add gradually — the mix should be thick but workable.

Do I need to remove the sonotube after pouring?

It’s optional. Above-ground portions are typically removed for appearance after the concrete sets. Below-ground tubes can remain in place as they’ll eventually decompose without affecting concrete strength.

How deep should deck footings be?

Footings must extend below your local frost line (12″ to 48″+ depending on climate). Most building codes require a minimum of 42″ in cold climates. Always check local codes before starting.

Can I pour concrete in cold weather?

Yes, but take precautions. Use fast-setting concrete, keep materials warm, and protect fresh concrete from freezing for at least 24 hours. Avoid pouring if temperatures will drop below 20°F within 24 hours.

Should I add rebar to sonotube footings?

For standard deck footings under 3 feet tall, rebar isn’t required. For taller columns or heavy-load applications, add vertical rebar (#4 or #5) extending into any structure above. Always check local building codes.

What’s the difference between quikrete and regular concrete?

Quikrete is a brand name for pre-mixed concrete. They offer both standard and fast-setting formulas. Fast-setting concrete sets in 20-40 minutes versus several hours for standard mix. Both achieve similar final strength.

How long before I can put weight on the footings?

Light loads (installing post brackets): 24-48 hours. Building structures: Wait 7 days for 50% strength. Maximum weight capacity: 28 days for full cure. Humid conditions and cooler temperatures slow curing.