Concrete Countertop Calculator
Work out the concrete for a cast countertop in cubic feet and 80 lb bags of countertop mix from its length, width and thickness.
How it works
cubic feet = (length ÷ 12) × (width ÷ 12) × (thickness ÷ 12) · bags = volume × 1.10 ÷ bag yield
Countertops are measured in inches, so every dimension is divided by 12 to get feet before multiplying into cubic feet. An 80-pound bag of specialized countertop mix yields about 0.6 cubic feet; ordinary sand mix works too but the pre-blended product is engineered for strength at 1.5–2 inch thickness. Add about 10% for the small amount lost in the mixer and for topping off the mold, and cast a little extra for test pieces.
Worked example
A 96 × 25 in top at 1.5 in: (96 ÷ 12) × (25 ÷ 12) × (1.5 ÷ 12) = 8 × 2.083 × 0.125 = 2.08 cubic feet. With 10% waste, 2.29 cu ft ÷ 0.6 per bag ≈ 4 bags.
Frequently asked questions
How thick should a concrete countertop be?
Cast tops are usually 1.5–2 inches, often with a thicker apparent edge created by the form. Thinner than 1.5 inches gets fragile unless it is reinforced with mesh or fiber and a proper countertop mix.
Can I use regular concrete mix?
A sand mix or high-strength mix can work, but purpose-made countertop mixes flow better, reach higher strength and shrink less, which matters at this thin cross-section. Whatever you use, reinforce it and seal the cured surface.
Why measure in cubic feet, not yards?
A countertop is a tiny volume — a fraction of a cubic yard — so cubic feet and bag counts are the practical units. Yards only make sense once you are ordering ready-mix by the truck.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.