Estimate cubic yards, bag count, and ready-mix cost for slabs, driveways, footings, and sonotubes. Enter your dimensions for an instant planning estimate.
Cubic yards, bags & cost
Covers spillage, uneven subgrade, and edge waste. 5% is typical for regular slabs. Increase to 10% for irregular shapes.
Results are planning estimates. Bag yield varies slightly by brand — check your product label. Confirm quantities with your concrete supplier before ordering.
Concrete is measured by volume. For slabs and footings, multiply length × width × depth to get cubic feet, then divide by 27 for cubic yards. Sonotubes use a cylinder formula. Always add a waste factor — 5% for regular slabs, 10% for irregular shapes or uneven ground.
Want the full formula with worked examples? Read our How to Calculate Concrete guide — covers every project type step by step.
One 80 lb bag yields about 0.60 cubic feet. One cubic yard = 27 cubic feet. So you need approximately 45 bags of 80 lb to make one cubic yard of concrete. Bag yield varies slightly by brand — always check your product label for the exact figure.
| Project Size | Best Option | Why |
|---|---|---|
| Under 1 yard | Bagged | No truck minimum |
| 1–3 yards | Either | Compare total cost |
| Over 3 yards | Ready-mix | Faster, cheaper per yard |
Use as a guide. Local soil conditions and building codes affect the correct depth for your project.
| Project | Typical Depth |
|---|---|
| Sidewalk or footpath | 3–4 inches |
| Patio or backyard slab | 4 inches |
| Residential driveway | 4–6 inches |
| Garage floor | 4–6 inches |
| Structural footing | 8–12 inches (varies) |
Project: Backyard patio 12 ft × 10 ft, 4 inches deep, 5% waste, 60 lb bags
At 1.56 cubic yards, compare ready-mix versus bagged. Also plan your gravel sub-base before pouring — typically 4 inches for a patio slab.
Need a deeper explanation? See our concrete calculation guide for more step-by-step examples.
Project: Deck footings — 12-inch diameter, 3.5 ft deep, 6 tubes, 5% waste, 60 lb bags
At 0.64 cubic yards, bagged concrete mixed on-site is the practical choice for most deck footing jobs. Confirm depth requirements with your local building code before pouring.
PSI (pounds per square inch) is the compressive strength of the concrete mix. When ordering ready-mix, your supplier will ask which strength you need. Higher PSI concrete costs slightly more per yard but is more resistant to cracking, heavy loads, and freeze-thaw damage. For bagged concrete, the PSI is printed on the bag — standard bags are typically 4,000 PSI.
Ask your local ready-mix supplier what is standard in your region — cold climates may require higher strength for freeze-thaw resistance.
| Project | Recommended PSI |
|---|---|
| Sidewalk or footpath | 3,000 PSI |
| Patio or backyard slab | 3,000–3,500 PSI |
| Residential driveway | 4,000 PSI |
| Garage floor | 4,000 PSI |
| Deck or structural footing | 4,000–5,000 PSI |
| Cold climate / freeze-thaw | 4,000–5,000 PSI |
Adding too much water weakens the final strength. Follow the bag instructions or your supplier's water ratio exactly — do not add extra water to make the mix easier to pour.
Concrete gains strength over 28 days. Pouring in very cold or very hot weather slows or disrupts curing. Keep the surface moist for the first few days after pouring.
Even high-PSI concrete will crack on an unstable base. A compacted gravel sub-base is as important as the mix itself — see the section below.
A compacted gravel sub-base is the most important factor in preventing concrete cracks. Concrete poured directly on soft soil, clay, or uncompacted fill will settle unevenly and crack — regardless of the PSI. Take time to prepare the base correctly before setting your forms.
Remove all grass, topsoil, and organic material from the area.
Grade the area with a slight slope for drainage — about ⅛ inch per foot away from structures.
Lay 4–6 inches of compacted crushed stone or gravel sub-base for driveways and garage floors. Patios on stable, well-draining soil may need 3–4 inches.
Compact the sub-base thoroughly with a plate compactor before setting forms.
Use our Gravel Calculator to estimate the sub-base material you need before starting your concrete project.
| Project | Sub-Base Depth |
|---|---|
| Patio or backyard slab | 3–4 inches |
| Sidewalk | 4 inches |
| Residential driveway | 4–6 inches |
| Garage floor | 4–6 inches |
Sonotube footings are set in undisturbed soil below the frost line, so a gravel sub-base layer is not usually required. Placing 2–3 inches of gravel at the bottom of the hole improves drainage. Always check your local frost depth and building code requirements.
Ready-mix begins to set once loaded and in transit. Forms must be built, sub-base compacted, and your crew in place before the truck arrives.
Most suppliers have a minimum order — typically around 1 cubic yard. Orders below the minimum may carry a short-load fee. Confirm with your supplier before ordering.
Let your supplier know whether you are pouring a driveway, patio, footing, or garage floor so they can recommend the correct PSI mix for your application.
Use this calculator to get your estimate, then confirm with your supplier. Always order slightly more than your estimate — running short mid-pour is a significant problem.
Enter your patio or slab dimensions to find out how many cubic yards or bags to order. Plan your gravel sub-base at the same time.
Switch to the Sonotube tab, enter your tube diameter, depth, and number of tubes. The bag count tells you exactly how many bags to pick up before you start.
Get a fast cubic yardage figure before writing a formal quote. Enter your price per yard for a cost estimate. For a full driveway cost breakdown, see our Driveway Cost Calculator.
Concrete driveways last longer but cost more upfront. Use our Asphalt Calculator to estimate tonnage and cost for the same project area and compare.
A 10 ft × 10 ft slab at 4 inches thick needs about 1.24 cubic yards before waste. With a standard 5% waste factor added, plan for around 1.30 cubic yards. At 6 inches thick, it needs approximately 1.85 cubic yards before waste. Use this calculator with your own dimensions to get an exact figure for your project.
A short-load fee is charged when you order less than the minimum load a ready-mix truck carries — usually around 1 cubic yard depending on the supplier. This fee can significantly increase the cost per yard on small orders, making bagged concrete more practical for small pours. Always ask your supplier about their minimum order and any short-load charges before ordering.
Residential driveways typically use 4,000 PSI concrete. In cold climates with freeze-thaw cycles, 4,000 PSI or higher is recommended. For a patio or sidewalk, 3,000–3,500 PSI is usually sufficient. Ask your local ready-mix supplier what is standard for your region. If you are considering asphalt instead, see our Asphalt Calculator to compare material quantities and cost.
Double-check your depth input — it must be in inches, not feet. Also verify that length and width are in feet. For sonotubes, diameter must be in inches and height in feet. Adding a 5–10% waste factor brings estimates closer to real-world requirements, especially for irregular shapes or uneven ground.
Concrete reaches about 70% strength in 7 days and full design strength in 28 days. Light foot traffic is usually safe after 24–48 hours. Avoid vehicle traffic for at least 7 days on a standard residential pour, and ideally 28 days before heavy loads. Keep the surface moist for the first few days to support proper curing.
Sonotube volume uses a cylinder formula: Volume = π × radius² × height × number of tubes. The radius is half the tube diameter converted to feet. For a 12-inch tube at 3.5 ft depth, the radius is 0.5 ft — giving about 2.75 cu ft per tube. Select the Sonotube tab in this calculator, enter your diameter in inches, height in feet, and number of tubes to get an instant result.
Estimate the compacted gravel sub-base you need before pouring a concrete slab or footing.
Compare asphalt vs concrete for your driveway — estimate asphalt tonnage and cost for the same area.
Get a full driveway cost estimate — material and labor — based on your own price inputs.