Project Hub

Concrete Project Hub

Cubic yard, bag count, slab thickness, and cost guides for a concrete slab, driveway, footing, or patio pour. Every calculator returns cubic yards, 60 lb and 80 lb bag counts, and a bulk-order size rounded to the nearest half yard.

Concrete is the material where measurement mistakes hurt most: a slab that runs an inch thick over 400 sq ft is another 1.2 cubic yards, or roughly 60 bags of 80 lb premix. Order too much and a short-load fee eats the savings; order too little and a truck return trip breaks the pour into a cold joint. This hub groups the concrete volume calculator with the reference guides that answer the questions people ask before a pour.

Start with the concrete volume calculator to convert your slab, footing, or driveway dimensions to cubic yards. Then read the slab-thickness and bags-per-yard guides to sanity-check the number against your project.

Start here

Concrete Volume Calculator

The core cubic-yard, bag-count, and cost calculator for any slab, footing, or driveway pour.

Calculators

CalculatorConcrete Volume CalculatorCubic yards and bag counts for slabs, footings, patios, and driveways.CalculatorPaver Base CalculatorCompacted crushed-stone base under a poured slab or paver install.CalculatorSand CalculatorBedding sand for pavers over a compacted base.CalculatorCubic Yard CalculatorUniversal volume converter for any bulk material.

Planning and reference guides

GuideHow Much Concrete Do I Need?GuideConcrete Bags per Yard GuideConcrete Slab Thickness Guide GuideConcrete Cost per Yard

Common questions

How many cubic yards of concrete do I need?: Cubic yards = (length ft x width ft x thickness in) / 324. A 12 x 12 patio at 4 inches is (12 x 12 x 4) / 324 = 1.78 cubic yards. Add 5 to 10 percent for waste and rounding.
How many 80 lb bags of concrete in a cubic yard?: About 45 bags of 80 lb premix per cubic yard. That is why anything above about 1 cubic yard is usually cheaper as ready-mix (with a short-load fee) than in bags.
Bags or ready-mix?: Under 1/2 cubic yard: bags. 1/2 to 1 cubic yard: still often bags because of ready-mix short-load fees. Above 1 cubic yard: ready-mix is almost always cheaper and produces a better slab.

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Construction Calculators

All build and repair estimators.

Sources and methodology

Cubic-yard volume uses the (length x width x thickness) / 324 formula. Bag counts use USDOT and manufacturer yields (0.45 cu ft per 60 lb bag, 0.6 cu ft per 80 lb bag). Waste percentages default to 5 to 10 percent. See our full methodology page for how we source and review each figure.

Last reviewed January 15, 2026.