Concrete Calculator

Calculate how much concrete you need in cubic yards. Estimate bags or ready-mix volume for slabs, footings, columns, and stairs.

Project Type

Slab Dimensions

ft
ft
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ft
in
in
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ft

Cost Options

$

Quick Reference

1 Cubic Yard
27 cubic feet
3 ft x 3 ft x 3 ft
80 lb Bag Coverage
0.6 cu ft
~45 bags per cubic yard
Ready-Mix Minimum
1 cubic yard
Short-load fees may apply
Waste Factor
+10%
Always add extra for spillage

Your Results

Calculated
Total Needed
0
cubic yards
With 10% Waste
0
cubic yards
Estimated Cost
$0
total

Detailed Breakdown

Volume in Cubic Feet 0
80 lb Bags Needed 0
60 lb Bags Needed 0
40 lb Bags Needed 0
Recommendation -

Key Takeaways

  • Concrete is sold by the cubic yard (27 cubic feet) for ready-mix delivery
  • Always add 10% extra for waste, spillage, and uneven subgrade
  • Projects over 1 cubic yard are usually more economical with ready-mix delivery
  • Standard slab thickness: 4 inches for patios, 6 inches for driveways
  • Allow 28 days for concrete to reach full strength

Understanding Concrete Calculations

Concrete is sold by the cubic yard (27 cubic feet) for ready-mix delivery or by the bag for smaller DIY projects. Accurately calculating your concrete needs prevents costly overages or project delays from running short.

Recommended Slab Thickness

Application Thickness Strength (PSI)
Sidewalks/Walkways 3-4 inches 3,000
Patios 4 inches 3,000
Residential Driveways 4-6 inches 3,500-4,000
Garage Floors 6 inches 3,500
Commercial/Heavy Use 6-8 inches 4,000+

Bags vs Ready-Mix

Bag Size Coverage Best For
40 lb bag 0.011 cu yd Small repairs
60 lb bag 0.017 cu yd Posts, small projects
80 lb bag 0.022 cu yd DIY slabs <1 cu yd
Ready-Mix Truck 1+ cu yd Projects >1 cu yd

Pro Tip: When to Order Ready-Mix

For projects requiring more than 1 cubic yard of concrete, ready-mix is generally more economical and ensures consistent quality. Most concrete trucks deliver a minimum of 1 cubic yard, with full trucks carrying 8-10 cubic yards. Expect to pay a short-load fee for orders under the minimum.

Concrete Tips for Success

  • Always add 10% extra for waste, spillage, and uneven subgrade
  • Prepare your forms and subgrade before concrete arrives
  • Have enough helpers ready - concrete waits for no one
  • Wet the subgrade before pouring to prevent moisture absorption
  • Use wire mesh or rebar for added strength
  • Allow proper curing time (7 days minimum, 28 days for full strength)
  • Keep concrete moist during curing with plastic or wet burlap

Weather Considerations

Temperature significantly affects concrete curing. Avoid pouring when temperatures will drop below 40F within 24 hours or rise above 90F. Hot weather accelerates setting time, while cold weather slows curing and can cause cracking. Ideal pouring conditions are 50-70F.

Frequently Asked Questions

How accurate are the results?
The Concrete applies a standard formula to your inputs — accuracy depends on how precisely you measure those inputs. For planning and estimation, results are reliable. For high-stakes or professional decisions, cross-check the output with a domain expert or primary source.
Can I use this on mobile?
Yes — the calculator is designed to work on any device. For complex multi-input calculations on small screens, landscape orientation gives more room to see all fields and results simultaneously.
How should I interpret the Concrete output?
The result is a calculated estimate based on the formula and your inputs. Compare it against the reference values or benchmarks shown on this page to understand whether your result is high, low, or typical. For decisions with real consequences, use the output as one data point alongside direct measurement and professional advice.
When should I use a different approach?
Use this calculator for quick, formula-based estimates. If your situation involves multiple interacting variables, time-varying inputs, or safety-critical decisions, consider a dedicated software tool, professional consultation, or direct measurement. Calculators are most reliable within their stated assumptions — check that your scenario matches those assumptions before relying on the output.