Building Materials

Concrete Calculator

Enter your project dimensions to estimate concrete volume, add a waste allowance, compare metric and US units, and work out ready-mix or premix-bag quantities.

Project dimensions

Choose a shape and enter the finished dimensions of the concrete you need.

Project shapeChoose based on geometry, not the project name. Rectangular works for slabs, pads, walls, footings, beams, rectangular columns and similar shapes. Round works for columns, piers, post holes, circular footings and similar shapes.

Length

Width

Thickness / depth / height

Waste allowance

Add extra material for uneven ground, spillage, form variation and small measurement errors.

Waste allowance

Purchase estimate

Optional. Estimate ready-mix cost or the number of premix bags to buy.

How are you buying concrete?

Price per volumePricing unit

Currency symbol or code

How to calculate concrete volume

For a rectangular slab, footing or wall, concrete volume is length × width × thickness. For a round column or post hole, the volume is π × radius² × depth. BuildAmounts converts each measurement to a common unit before calculating the result.

Rectangular concreteVolume = length × width × depth

Round concreteVolume = π × (diameter ÷ 2)² × depth

Why add a waste allowance?

Real projects rarely match perfect mathematical dimensions. Uneven excavation, form movement, spillage and small measuring differences can increase the actual amount used. The calculator starts with a 10% allowance, but you can change it to suit your project.

Premix bag quantities

The preset bag yields are approximate examples for common QUIKRETE Concrete Mix sizes: 40 lb ≈ 8.5 L, 50 lb ≈ 10.6 L, 60 lb ≈ 12.7 L, 80 lb ≈ 17 L and 90 lb ≈ 19.1 L of mixed concrete. Product yields vary, so use the custom-yield option when your manufacturer lists a different value.

Reference: QUIKRETE Concrete Mix No. 1101 data sheet.

Before ordering concrete

This calculator is a planning estimate, not a guarantee of the quantity required on site. Check your final dimensions, supplier minimums, truck-load policies, product yield and local construction requirements before ordering or pouring concrete.