Concrete Calculator

At 4 inches thick: 10 × 10 × (4÷12) = 33.333 ft³ ≈ 1.23 yd³ (about 56 eighty-pound bags before allowance). At 6 inches: 50 ft³ ≈ 1.85 yd³ (about 84 eighty-pound bags). Use slab mode for your exact thickness, quantity, and optional safety allowance.

At 4 inches: 12 × 12 × (4÷12) = 48 ft³ ≈ 1.78 yd³. At 6 inches: 72 ft³ ≈ 2.67 yd³. Bag counts depend on bag yield—enter the same dimensions in the calculator for 40/50/60/80 lb estimates.

At 4 inches: 20 × 20 × (4÷12) = 133.333 ft³ ≈ 4.94 yd³. At 6 inches: 200 ft³ ≈ 7.41 yd³. Larger pours are usually ordered as ready-mix by the cubic yard rather than bags.

Cubic feet = length(ft) × width(ft) × (4÷12). Cubic yards = cubic feet ÷ 27. A quick planning shortcut for 4-inch slabs is square footage ÷ 81 ≈ cubic yards (because 27 ÷ (4/12) = 81). Always confirm with the full calculator when thickness, quantity, or allowance differs.

Cubic feet = length(ft) × width(ft) × (6÷12) = length × width × 0.5. Cubic yards = cubic feet ÷ 27. One cubic yard covers about 54 sq ft at 6 inches thick (27 ÷ 0.5 = 54).

Pros often divide total square footage by 81 to estimate cubic yards for a 4″ pour. Example: 200 sq ft ÷ 81 ≈ 2.47 yd³. Use a safety allowance so you do not run short—required thickness still depends on loads, soil, reinforcement, and local requirements.

For a continuous footing with length in feet and width/depth in inches: cubic feet = length(ft) × (width_in÷12) × (depth_in÷12). Example: 20 ft × 12 in × 12 in = 20 ft³ ≈ 0.74 yd³ (about 34 eighty-pound bags). Use Footing mode and set Quantity for multiple identical pads.

Convert diameter and height to feet, then volume = π × (diameter÷2)² × height. Example: 12 in diameter × 48 in tall → radius 0.5 ft, height 4 ft → ≈ 3.14 ft³ ≈ 0.12 yd³ (about 6 eighty-pound bags). Multiply by Quantity for several identical piers.

Calculate one item, then multiply by Quantity (or set Quantity in the calculator). Eight identical 12 in × 48 in piers need about 8 × 3.14 = 25.13 ft³ before any safety allowance. Bag and yard totals scale with the adjusted volume.

Use Round Column/Pier mode with each pier’s diameter and height (or embedment depth), then set Quantity to the number of posts. Add a safety allowance for uneven excavation. Confirm pier size with your deck plan or local code—this tool estimates volume, not structural design.

It depends on bag yield. At typical approximate yields: about 90 of the 40 lb bags (0.30 ft³), 72 of the 50 lb bags (0.375 ft³), 60 of the 60 lb bags (0.45 ft³), or 45 of the 80 lb bags (0.60 ft³) per cubic yard (27 ft³). Always verify the yield printed on your bag.

An 80 lb bag that yields about 0.60 ft³ needs approximately 45 bags for one cubic yard (27 ÷ 0.60 = 45). Actual yield varies by product—check the manufacturer’s stated yield.

At an approximate yield of 0.45 ft³ per 60 lb bag, one cubic yard requires about 60 bags (27 ÷ 0.45 = 60). Confirm the yield on your specific mix.

At an approximate yield of 0.30 ft³ per 40 lb bag, one cubic yard requires about 90 bags (27 ÷ 0.30 = 90). Product yields differ—use the bag label when ordering.

Coverage depends on thickness. One cubic yard (27 ft³) covers about 162 sq ft at 2 in, 108 at 3 in, 81 at 4 in, 64.8 at 5 in, 54 at 6 in, 40.5 at 8 in, and 27 at 12 in. Formula: coverage_sqft = 27 ÷ (thickness_in ÷ 12).

About 81 sq ft. Calculation: 27 ft³ ÷ (4÷12 ft) = 81 sq ft per cubic yard at 4 inches thick.

About 54 sq ft. Calculation: 27 ft³ ÷ (6÷12 ft) = 54 sq ft per cubic yard at 6 inches thick.

Normal-weight concrete is commonly around 3,900–4,050 lb per cubic yard depending on the mix. This calculator’s approximate weight uses about 4,000 lb/yd³ (≈148 lb/ft³). Actual density varies by mix design and aggregate.

Usually yes. Measurement variation, uneven subgrade, spillage, form variation, and placement loss can leave you short. Use Extra / safety allowance (%) so adjusted volume = base × (1 + allowance% ÷ 100). Many projects use a modest buffer rather than ordering the exact calculated amount.

There is no single correct percent—it depends on site conditions and placement method. Enter a safety allowance in the calculator (often a small percentage for simple pads; more when excavation or forms are irregular). Do not force a non-zero default; choose a buffer that matches your risk of running short.

Divide cubic feet by 27. Example: 33.333 ft³ ÷ 27 ≈ 1.23 yd³. The calculator shows cubic feet, cubic yards, and cubic meters from the same exact volume.

Switch to Metric mode (m / cm inputs) or convert from cubic feet: 1 ft³ = 0.028316846592 m³ and 1 yd³ = 0.764554857984 m³. Switching units converts your current project rather than replacing it with unrelated defaults.

Larger jobs such as driveways and garage slabs are usually easier with ready-mix by the yard. Smaller pads, footings, and piers are often practical with 40, 50, 60, or 80 lb bags. This tool shows both cubic yards and bag estimates so you can compare options.

It applies standard geometric volume formulas with full internal precision and rounds only for display. Results are planning estimates—real orders also depend on excavation, forms, reinforcement, mix, and placement. Verify bag yields and supplier quantities before purchasing.

Yes. Extra / safety allowance (%) defaults to 0%. When you enter a percentage, bag counts, recommended yards, and approximate weight use the adjusted volume. Base volume before allowance remains visible when an allowance is set.