Concrete Calculator

Calculate how much concrete you need for slabs, columns, walls, and stairs. Get cubic yards, bags needed, waste factors, and cost estimates for any project.

Cubic Yards

0.00

(0.00 + 10% waste)

Cubic Feet

0.00

Cubic Meters

0.00

Estimated Cost

$0.00

@ $150/yd³

Bags Needed (Pre-Mixed Concrete)

40 lb bags

0

0.30 cu ft each

60 lb bags

0

0.45 cu ft each

80 lb bags

0

0.60 cu ft each

Recommended Concrete Thickness

ApplicationImperialMetric
Sidewalk4"10 cm
Patio4"10 cm
Driveway6"15 cm
Garage Floor6"15 cm
Foundation Wall8"20 cm
Footer / Footing12"30 cm
Structural Column12"30 cm
Retaining Wall8-12"20-30 cm

How to Use the Concrete Calculator

This calculator helps you estimate the amount of concrete needed for any project. Select the shape of your pour, enter the dimensions, and get instant results in cubic yards, cubic feet, and cubic meters. You can add multiple sections to calculate combined totals for complex projects.

Supported Shapes

  • Slab / Square: For patios, sidewalks, driveways, and garage floors. Enter length, width, and depth.
  • Cylinder / Column: For round columns, piers, sono tubes, and post holes. Enter diameter and height.
  • Wall / Footer: For foundation walls, retaining walls, and footings. Enter length, height, and wall thickness.
  • Stairs: For concrete steps. Enter the number of steps, rise, run, and total stair width.

Tips

  • Always order 5-10% more concrete than calculated to account for waste and uneven ground.
  • For ready-mix delivery, most companies have a minimum order of 1 cubic yard and may charge short-load fees for small orders.
  • One 80 lb bag of pre-mixed concrete yields approximately 0.6 cubic feet of cured concrete.

Frequently Asked Questions

How do I calculate how much concrete I need?+
Measure the length, width, and depth (thickness) of your project area. Multiply these three dimensions together to get the volume. For rectangular slabs, use length x width x depth. For cylinders, use pi x radius squared x height. Always add 5-10% extra for waste, spillage, and uneven subgrade.
How many bags of concrete do I need?+
First calculate total cubic feet needed. Then divide by the bag yield: a 40 lb bag covers 0.30 cu ft, a 60 lb bag covers 0.45 cu ft, and an 80 lb bag covers 0.60 cu ft. For example, a 4-inch thick 10x10 ft slab requires about 33.3 cu ft, which is approximately 56 bags of 80 lb concrete mix.
How thick should my concrete slab be?+
Sidewalks and patios typically require 4 inches of concrete. Driveways and garage floors should be 6 inches thick. Foundation walls are usually 8 inches, and footings or footers are typically 12 inches thick. Heavier loads and vehicular traffic require thicker slabs.
What is the difference between cubic yards and cubic feet of concrete?+
One cubic yard equals 27 cubic feet. Ready-mix concrete from a truck is typically sold by the cubic yard, while bagged concrete is measured in cubic feet. To convert cubic feet to cubic yards, divide by 27. For example, 81 cubic feet equals 3 cubic yards.
How much does a yard of concrete cost?+
Ready-mix concrete typically costs between $120 and $200 per cubic yard delivered, depending on your location, the type of mix, and delivery distance. Short-load fees may apply for orders under 5-10 yards. Specialty mixes, fiber reinforcement, or accelerated curing can add $10-30 per yard.
Should I add extra concrete for waste?+
Yes, always add a waste factor of 5-10% to your calculated volume. This accounts for spillage, uneven subgrade, form irregularities, and over-excavation. For complex shapes like stairs or irregular forms, consider adding 10-15% extra. It is always better to have slightly more concrete than to run short during a pour.
When should I use bags vs. ready-mix concrete?+
Bagged concrete is best for small projects under 1 cubic yard, such as setting fence posts, small pads, or repairs. For projects over 1-2 cubic yards, ready-mix delivery is more cost-effective and practical. Mixing more than 40-50 bags by hand is extremely labor-intensive.

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Concrete Calculator — free online concrete calculator, concrete yard calculator, concrete slab calculator, how much concrete do I need, concrete bag calculator, cubic yard calculator, concrete cost estimator, concrete stair calculator, concrete column calculator, concrete footer calculator. No signup required. Works in your browser.