MeasureMaterial

Concrete Calculator

Estimate concrete volume for a rectangular slab or pour, then convert to cubic yards and optional bag counts.

Slab thickness or pour depth.

Extra material for cuts, spillage, and irregular areas.

Cubic feet one bag yields. Check your bag label — yields vary by product.

How to use

Enter length, width, and depth with units, set waste, confirm bag yield from your product label if you need bags, then calculate.

How the calculation works

Enter length, width, and depth with units. The calculator converts dimensions to feet, multiplies for cubic feet, converts to cubic yards, applies waste, and optionally estimates bags from your bag yield.

Formula

volume_ft³ = length_ft × width_ft × depth_ft; volume_yd³ = volume_ft³ ÷ 27; adjusted = volume × (1 + waste%/100); bags = ceil(adjusted_ft³ ÷ bag_yield_ft³)

Example calculation

A 10 ft × 10 ft slab at 6 in thick is 50 ft³ (about 1.85 yd³) before waste.

Assumptions

  • Shape

    Simple rectangular pour

    Material: concrete · Key: geometry

    Does not model footings, steps, or irregular edges.

    Source: Geometric model

  • Default waste (%)

    10%

    Material: concrete · Key: waste

    Adjust for placement method and site conditions.

    Source: Planning default — not a code requirement

  • Default bag yield (ft³ / bag)

    0.6 ft³ per bag

    Material: concrete · Key: bag_yield

    Roughly aligned with common 80 lb bag class yields published by various brands; yields vary by mix. Always use the bag label.

    Source: Planning default — confirm with your product label or supplier quote. Not a lab or manufacturer certification.

Practical notes

  • Order a little extra when access is difficult or the subgrade is uneven.
  • Ready-mix is usually ordered in cubic yards; bags are useful for small pours.
  • Confirm bag yield on the package — it is not the same for every product.

Limitations

  • This is a planning estimate, not a professional takeoff.
  • Reinforcement, forms, slope, and voids can change real needs.
  • Bag yields vary by manufacturer and mix.

FAQ

How do I convert inches of thickness?
Choose inches for depth (for example 4 or 6). The calculator converts thickness to feet before multiplying volume.
Should I trust the bag estimate?
Use it only after setting bag yield from your product label. Treat the result as an estimate and round up for purchase.
Is waste required?
Waste is configurable. Many DIYers start around 5–10% depending on the pour.

Related calculators

Results are planning estimates. See the Calculator Disclaimer.