Concrete Volume Calculator

Instantly estimate cubic yards, cubic meters, and pre-mixed bag counts for slabs, driveways, and pads. Adjust waste margin for spillage and uneven subgrade.

Project Dimensions

Length

Width

Thickness

Waste Margin Allowance10%

0%30%

Live Results

Cubic Yards

1.36

Cubic Meters

1.04

60 lb Bags

80 lb Bags

Includes 10% waste allowance · Bags rounded up

How to Use This Calculator

Measure your pour area. Measure the length and width of your slab, driveway, or pad in feet. Use a tape measure at the longest points.
Set slab thickness. Enter thickness in inches or feet. Use 4 inches for patios, 5–6 inches for residential driveways, and 6–8 inches for heavy-load pads.
Adjust waste margin. Set a waste allowance of 10% for standard pours. Increase to 15–20% for complex forms, pump placements, or uneven subgrade.
Read your order quantities. Review cubic yards for ready-mix trucks and bag counts for DIY pours. Round up partial bags and add a half-yard buffer on truck orders.

Formula & Example

Concrete volume starts with a simple rectangular prism formula: multiply length × width × thickness to get the base volume in cubic feet. If thickness is entered in inches, it is converted to feet by dividing by 12 before the calculation runs.

Base Volume (cu ft) = Length (ft) × Width (ft) × Thickness (ft)

Adjusted Volume = Base Volume × (1 + Waste % ÷ 100)

Cubic Yards = Adjusted Volume ÷ 27

Cubic Meters = Adjusted Volume × 0.0283168

Worked Example

A 10 ft × 10 ft patio slab at 4 inches thick: Base volume = 10 × 10 × (4 ÷ 12) = 33.33 cu ft. With 10% waste: 33.33 × 1.10 = 36.67 cu ft. Cubic yards = 36.67 ÷ 27 = 1.36 CY. At 0.60 cu ft per 80 lb bag, that requires 62 bags (rounded up).

Pre-mixed bag counts assume standard yields of 0.45 cu ft per 60 lb bag and 0.60 cu ft per 80 lb bag (Quikrete/Sakrete). Results are always rounded up to the nearest whole bag.

Reference Data: Recommended Thickness

Project Type	Recommended Thickness
Slabs (patios, shed bases)	4 inches (0.33 ft)
Driveways (residential)	5–6 inches
Commercial pads / heavy load	6–8 inches

Frequently Asked Questions

How many 80lb bags of concrete do I need for a 10×10 slab?▾

A 10 ft × 10 ft slab at 4 inches thick equals 33.3 cu ft of concrete. With a 10% waste allowance, you need roughly 36.7 cu ft — about 62 eighty-pound bags (at 0.60 cu ft each) or 82 sixty-pound bags. That is approximately 1.36 cubic yards. For a ready-mix truck, order 1.5 yards to be safe.

How thick should a concrete driveway be?▾

Residential driveways typically require 5–6 inches of concrete over a compacted gravel base. Standard passenger vehicles are fine at 4 inches, but driveways that see trucks, RVs, or heavy equipment should use 6 inches with rebar or wire mesh reinforcement. Commercial pads and loading areas often call for 6–8 inches with proper steel reinforcement per local code.

How much does a cubic yard of concrete cover?▾

One cubic yard (27 cu ft) covers approximately 81 sq ft at 4 inches thick, 54 sq ft at 6 inches thick, or 40.5 sq ft at 8 inches thick. Use these benchmarks to quickly sanity-check your order before calling the ready-mix plant.

Should I order ready-mix or use bagged concrete?▾

Ready-mix is more cost-effective above roughly 1 cubic yard. Bagged concrete suits small pads, post holes, and repair work. A 10×10 patio at 4 inches needs about 1.36 yards — borderline where a short-load truck fee may apply. Compare local short-load pricing against bag costs before deciding.

How much does a yard of concrete cost?▾

Ready-mix concrete typically runs $125–$175 per cubic yard delivered, varying by region, PSI mix, and fuel surcharges. Bagged concrete costs more per yard but avoids minimum load fees. Always confirm current plant pricing and whether delivery fees apply to small orders.

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