Concrete Calculator

Planning a driveway, patio, or post? Accurately estimate the volume and bags of premix needed for your project.

Volume Needed

0.00

Cubic Yards

(0.0 Cubic Feet)

80lb Bags

0

60lb Bags

0

Bag estimates are approximate. Always buy 10% extra for waste.

How to Calculate Concrete

Concrete is typically measured in Cubic Yards. One cubic yard is 27 cubic feet.

Formulas

  • Slab / Rectangular:Length (ft) × Width (ft) × Depth (ft) = Cubic Feet
  • Column / Circular:π × Radius² (ft) × Height (ft) = Cubic Feet

Pro Tip: The Safety Margin

Always order or buy 5-10% more than the exact calculation to account for spillage, uneven ground, or calculation errors. It's much better to have a little left over than to run out mid-pour!

Understanding Concrete Mixes

Not all concrete is the same. The strength is measured in PSI (Pounds per Square Inch).

  • Standard Mix (2500-3000 PSI): Good for walkways, patios, and residential floors.
  • High-Strength (4000+ PSI): Required for driveways, garage floors, and foundations that bear heavy loads.
  • Fast-Setting: ideal for setting posts (mailboxes, fence posts) where you need it to harden in 20-40 minutes.

Curing vs. Drying

Many beginners mistake drying for curing. Concrete doesn't harden by drying out; it hardens by a chemical reaction with water called hydration.

If concrete dries too fast (on a hot, windy day), the reaction stops, and the concrete becomes weak and powdery. To "cure" concrete properly, keep it moist for at least 3-7 days by misting it with water or covering it with plastic.

Frequently Asked Questions

You need approximately forty-five (45) 80lb bags to make 1 cubic yard of concrete. If using 60lb bags, you need about 60 bags.