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Concrete Calculator

Estimate concrete yards, bags, and compacted base for patios, sidewalks, small pads, slabs, and residential driveways.

Interactive slab planner

Concrete slab preview

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Sample patio preview
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Your estimate

-- cu yd ready-mix

Enter a project area to see cubic yards, bags, and base material.

Order list

  • MIXReady-mix concreteSelected path: order by cubic yard--
  • ALTBagged mix alternativeComparison only; do not order both paths--
  • BASECompacted gravelSuppliers may quote by cubic yard or ton--

Prep list

  • CUTSSaw cuts10 ft spacing, 1 in deep--
  • DIGDig depth if flush to grade4 in slab + 4 in base - 0 in above grade--
  • BASEBase prepCompact aggregate and confirm drainage before the pour--
  • CHECKPlanning noteMaterial planner only; not structural, permit, or code guidanceReview

Need the slab area first?

Trace the patio, driveway, walkway, or pad on the satellite map, then use the square footage here.

Measure on the map
How the estimate is calculated

Concrete volume is area multiplied by slab depth. The calculator adds your buffer before converting to cubic yards and bags.

Concrete cubic feet = area × (slab depth ÷ 12)

Total concrete = concrete cubic feet + buffer

Cubic yards = total concrete cubic feet ÷ 27

Bags = total concrete cubic feet ÷ bag yield, rounded up

Base tons = base cubic yards × 1.5

Dig depth = slab depth + base depth - finished height above grade

Planning checks

Ready-mix

Call with cubic yards and ask about minimum loads, truck access, and chute reach.

Bagged mix

Use bags for small pads and repairs. Larger slabs become a lot of lifting and mixing.

Prep

Compact the base, plan drainage, and keep control-joint panels close to square.

Driveways

Heavy loads, weak soils, reinforcement, or permits need local guidance.

Planning beds too? Calculate mulch.

Concrete calculator FAQ

How do I calculate concrete for a slab?

Measure the area in square feet, multiply by slab depth in feet, then divide cubic feet by 27 for cubic yards. This calculator adds your selected extra concrete before rounding bags up.

How thick should a patio or sidewalk slab be?

Four inches is a common planning depth for patios, walkways, and small pads on a properly prepared base. Local conditions, loads, and codes can change that.

How thick should a driveway slab be?

Residential driveways often plan around 5 to 6 inches depending on vehicle loads and base prep. Heavy vehicles, poor soil, or local requirements may need a stronger design.

How many 80 lb bags are in a cubic yard of concrete?

An 80 lb bag commonly yields about 0.6 cubic feet. One cubic yard is 27 cubic feet, so a cubic yard is about 45 bags before any extra buffer.

Should I order extra concrete?

A 10% buffer is a practical starting point for uneven grade, spillage, and small measurement differences. Ready-mix suppliers may also recommend a minimum extra amount.

Is this calculator for foundations or building slabs?

No. This is a material planner for residential flatwork such as patios, sidewalks, small pads, slabs, and driveways. Structural work needs local code and professional guidance.

Should I measure the slab area on the map first?

Use the satellite map when the patio, driveway, walkway, or pad shape is irregular. A traced outline is better than a length × width estimate for real orders.

Trace the slab area

Use the satellite map for patios, pads, walkways, or driveways that do not fit a simple length × width estimate.

Start measuring