MaterialSum

Concrete Calculator

Enter your project dimensions to find out how much concrete you need — in cubic yards, cubic meters, or bags of Quikrete-style mix.

Dimensions
ft
ft
in
Material & Waste
Optional Cost
Enter your measurements above to see results.

How to use the Concrete Calculator

  1. Pick the project type that matches your pour (slab, wall, footing, round column, or circular pad).
  2. Enter the dimensions. Use inches for thickness and feet for lengths.
  3. Add a waste allowance — 10% covers spillage and uneven subgrade for most pours.
  4. Optionally enter bag or ready-mix prices to see an estimated cost.

Formula & methodology

Volume = Area × Depth. For a slab: length × width × thickness. For a round column: π × (diameter ÷ 2)² × height. 1 cubic yard = 27 cubic feet. Bag yields: 80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 40 lb ≈ 0.30 ft³ of mixed concrete.

Example

A 10 ft × 10 ft slab at 4 in thick: 10 × 10 × 0.333 ft = 33.3 ft³ ≈ 1.23 cu yd. With 10% waste, order about 1.36 cu yd — or 57 bags of 80 lb mix.

Related calculators

Sonotube Concrete CalculatorDeck posts, mailboxes, footings — enter tube diameter, depth, and quantity to get the concrete you need.Concrete Cost CalculatorEnter your slab dimensions and local pricing to see what the pour will actually cost — including the delivery fee that surprises everyone.Sand CalculatorEnter area and depth to get the amount of sand you need — by volume, weight, or 50 lb bags.Paver CalculatorEnter your patio or path dimensions and paver size to get the number of pavers — plus optional bedding sand and gravel base quantities.

FAQ

How many 80 lb bags of concrete make a yard?

It takes about 45 bags of 80 lb mix to make one cubic yard (27 ft³ ÷ 0.60 ft³ per bag). For anything over roughly 1 yard, ready-mix delivery is usually cheaper and far less work.

How thick should a concrete slab be?

Patios and walkways are commonly 4 inches; driveways often use 4–6 inches. This calculator measures volume only — check local codes or ask an engineer for structural requirements.

Why add a waste allowance?

Spillage, uneven ground, and settling at the edges typically consume 5–10% extra. Ordering short is far more expensive than ordering 10% heavy.

Should I calculate in cubic yards or bags?

Use bags for small pours (under about 0.5–1 yard) and ready-mix cubic yards for larger jobs. The calculator shows both.

Note: This tool estimates volume only. It is not structural engineering advice — for load-bearing slabs, footings, or permits, consult a qualified professional.