How do I calculate concrete needed?

Measure length × width × thickness (in feet), divide by 27 to get cubic yards. For a 10ft × 10ft × 4" slab: (10 × 10 × 0.33) / 27 = 1.22 cubic yards. Always add 10% for waste.

How thick should a concrete slab be?

Standard thickness: 4" for residential slabs and sidewalks, 5-6" for driveways and garage floors, 6-8" for heavy equipment areas. Thicker concrete provides more strength and durability.

How much does a yard of concrete cost?

Concrete costs $125-175 per cubic yard delivered (2025 average). Factors affecting price: location, additives, delivery distance, and order size. Minimum delivery charges often apply for small orders.

How many bags of concrete do I need?

One 80lb bag = 0.6 cubic feet (45 bags per yard). One 60lb bag = 0.45 cubic feet (60 bags per yard). For small jobs under 1 yard, bagged concrete is convenient. For larger projects, order ready-mix.

Should I order extra concrete?

Yes, always add 5-10% waste factor for ground variations, spillage, and over-excavation. Better to have extra than run short mid-pour. You cannot add concrete later once it begins setting.

Concrete Calculator

Calculate cubic yards of concrete needed for slabs and footings

Concrete Calculator

Calculate cubic yards of concrete needed for slabs, footings, and driveways. Get bag quantities and cost estimates instantly.

Project Shape

Length *

Length of the slab or footing

Width *

Width of the slab or footing

Thickness *

inches

4 inches standard, 5-6 inches driveways, 6-8 inches heavy loads

Waste Factor

10% recommended for safety margin

How to Calculate Concrete

Calculating concrete is straightforward: measure the length, width, and thickness of your project, then convert to cubic yards (the standard unit for ordering concrete).

Step-by-step formula:

Measure length and width in feet
Measure thickness in inches, convert to feet (divide by 12)
Calculate cubic feet: Length × Width × Thickness
Convert to cubic yards: Cubic Feet ÷ 27
Add 10% waste factor for safety

Example: A 10ft × 12ft × 4" slab:
(10 × 12 × 0.33) ÷ 27 = 1.48 cubic yards
With 10% waste: 1.48 × 1.1 = 1.63 cubic yards to order

Concrete Thickness Guidelines

Choose the right thickness for your project:

4"Residential slabs & sidewalks: Standard for patios, walkways, and shed floors
5-6"Driveways & garage floors: Handles vehicle weight without cracking
6-8"Heavy equipment areas: Commercial or industrial applications
8-12"Footings & foundations: Structural support for buildings

Always check local building codes for minimum thickness requirements in your area.

Frequently Asked Questions

Everything you need to know about this tool