CH
CalcHub

Concrete Calculator

Whether you're pouring a patio slab, setting fence post footings, or building a foundation wall, knowing exactly how much concrete to order saves money and prevents waste. Enter your project dimensions below to get an instant estimate in cubic yards and pre-mixed bags.

Enter Your Measurements

Results

Enter your measurements to see results

How to Use This Calculator

  1. Measure the length and width of your project area in feet.
  2. Measure the depth or thickness in inches.
  3. Enter the values above and review the results.
  4. Optionally enter a price per cubic yard to see estimated material cost.
  5. Add 5–10% to the result for waste and spillage.

How Concrete Calculation Works

This calculator converts your length, width, and depth measurements into cubic feet, then divides by 27 to get cubic yards — the standard unit concrete suppliers use. It also estimates the number of pre-mixed bags you would need if mixing by hand. The bag estimates use industry-standard yields: a 40 lb bag yields about 0.30 cubic feet, a 60 lb bag about 0.45 cubic feet, and an 80 lb bag about 0.60 cubic feet of cured concrete. For ready-mix delivery, most suppliers have a minimum order (often 1 yard) and charge extra for short loads under 5-10 yards.

Formula

Volume (cubic feet) = Length (ft) × Width (ft) × Depth (in) ÷ 12. Then divide by 27 to convert to cubic yards. A 40 lb bag covers ~0.011 yd³, a 60 lb bag covers ~0.017 yd³, and an 80 lb bag covers ~0.022 yd³. Always add 5–10% extra for waste.

Frequently Asked Questions

How many bags of concrete do I need for a 10×10 slab?
A 10×10 foot slab at 4 inches thick requires about 1.24 cubic yards of concrete. That's approximately 56 bags of 80 lb concrete mix, 67 bags of 60 lb mix, or 112 bags of 40 lb mix. For a project this size, ordering ready-mix delivery is usually more cost-effective than buying bags.
How much does a yard of concrete cost?
Ready-mix concrete typically costs $100–$200 per cubic yard depending on your location, the mix strength, and delivery distance. Short load fees (for orders under 5–10 yards) can add $50–$100. Pre-mixed bags cost more per yard but are practical for small projects.
How thick should a concrete slab be?
Standard residential slabs (patios, walkways) are 4 inches thick. Driveways should be at least 5–6 inches. Garage floors typically need 6 inches. For heavy loads, increase thickness and add rebar or wire mesh reinforcement.
How much extra concrete should I order?
Order 5–10% more than your calculated amount. Concrete is difficult to match if you run short mid-pour, and the cost of a little extra is far less than the hassle of a second delivery or batch.
What is the difference between concrete and cement?
Cement is one ingredient in concrete. Concrete is the finished product made from cement, water, sand, and gravel (aggregate). When people say 'cement mixer' or 'cement slab,' they usually mean concrete.

Related Calculators

Rebar Calculator

Calculate rebar quantity, spacing, and weight for concrete slabs and footings.

Brick Calculator

Calculate how many bricks you need for walls, patios, and walkways.

Gravel Calculator

Calculate how much gravel you need in tons and cubic yards for driveways, paths, and landscaping.

Paver Calculator

Calculate how many pavers you need for patios, walkways, and driveways.