How many 80 lb bags of concrete equal one cubic yard?

One 80-lb bag yields approximately 0.60 cubic feet. One cubic yard = 27 cubic feet, so you need about 45 bags (27 ÷ 0.60 = 45) per cubic yard. For 60-lb bags: 60 bags per yard (27 ÷ 0.45). Pre-mixed bags become expensive for anything over about 0.5 cubic yards — ready-mix is more economical for larger pours.

How thick should a concrete slab be?

For foot traffic only (patios, walkways): 4 inches minimum. For vehicle traffic (driveways): 6 inches minimum, 8 inches for heavy vehicles. Garage floors: 4–6 inches. Structural slabs with rebar: consult an engineer. Footings: width typically 2× foundation width, depth to below frost line (varies by climate — up to 48 inches in cold climates).

What is the typical price of ready-mix concrete?

Ready-mix concrete prices vary by region and market conditions, typically ranging from $110–$175 per cubic yard. Short loads (under 5 yards) often incur an additional short-load fee of $50–$150. There may also be Saturday/overtime delivery charges and fuel surcharges. Get quotes from multiple suppliers and ask about short-load minimums.

How long does it take for concrete to cure?

Concrete gains strength continuously over time. It reaches approximately 70% of its 28-day strength in the first 7 days. It can bear foot traffic after 24–48 hours, vehicle traffic after 7 days, and full heavy-load capacity after 28 days. Keep it moist (cure it) for at least 7 days by covering with plastic sheeting or applying a curing compound.

🔧Utilities

How Much Concrete Do You Need? Concrete Volume Calculator

How much concrete do you need?

What This Does

Ordering the right amount of concrete is critical for any construction project — order too little and your pour is interrupted, order too much and you're paying for waste. Concrete is typically ordered by the cubic yard (27 cubic feet) from ready-mix suppliers, or in pre-mixed bags for smaller projects. Getting the volume right before ordering saves time, money, and the logistical nightmare of a mid-pour shortage. The calculation varies by shape. For slabs and footings: Volume = Length × Width × Thickness. For circular slabs or columns: Volume = π × radius² × depth. For steps: each step is calculated as a rectangular volume, then summed. All dimensions must be in consistent units before calculating, and the result is converted to cubic yards by dividing by 27 (since 1 cubic yard = 27 cubic feet). A critical professional practice: always add 5–10% to your calculated volume for waste, spillage, and uneven forms. Concrete is difficult to work with when running short — small pours take time to set, and adding fresh concrete to partially-set concrete creates weak joints. This calculator includes the waste factor in its recommendations. Pre-mixed bags are practical for small jobs: 60 lb bags yield 0.45 cubic feet, 80 lb bags yield 0.60 cubic feet. This calculator shows how many bags you'd need, though ready-mix is more economical for anything over 0.5 cubic yards.

When Should You Use This?

→Planning a concrete slab for a patio, driveway, garage floor, or shed foundation
→Calculating concrete for footings, piers, or columns for a deck or structure
→Estimating bags of concrete needed for small projects like fence posts or steps
→Checking your concrete order before calling a ready-mix supplier
→Estimating project cost before getting formal quotes

Example Scenario

Jason is pouring a 20' × 12' patio at 4" depth. Volume: 20 × 12 × (4/12) = 80 cubic feet = 2.96 cubic yards. With 10% waste: 3.26 cubic yards — round up to 3.5 cubic yards order. In 80-lb bags: 3.26 × 27 / 0.6 = 147 bags (not practical — he'll call for ready-mix). Estimated cost at $140/yard: $490 for the concrete order.

Concrete Calculator

How Much Concrete Do You Need?

Calculate cubic yards, bags, and cost for slabs, footings, columns, and steps.

Length (ft)

Width (ft)

Thickness (in)

Min 4" patios · 6" driveways

Waste Factor (%)

Recommend 5–10%

Ready-Mix Price ($/yd³)

Typical: $110–$175/yd³

About This Calculator

Ordering the right amount of concrete is critical — too little interrupts your pour, too much wastes money. Concrete is ordered in cubic yards (1 yd³ = 27 ft³) from ready-mix suppliers, or in pre-mixed bags for smaller projects. This calculator handles slabs, footings, columns, and steps, and always recommends a waste factor to protect against mid-pour shortages.

The core formula is Volume = Area × Depth (or π × r² × height for columns). All dimensions convert to feet before multiplying, then divide by 27 to get cubic yards. The waste factor compensates for spillage and uneven form bottoms — running short mid-pour creates a cold joint, a structural weak point in the finished slab.

For small pours under 0.5 cubic yards, bags are practical. At 0.5–1 cubic yards, call a supplier and ask about short-load fees. Over 1 cubic yard, ready-mix from a batch plant is almost always more economical and consistent. Always specify your required PSI and whether you need air-entrained concrete for freeze-thaw climates.

Results are for informational purposes only.