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Calculators & guides

Concrete Slab Cost Calculator

Price a patio, shed base or garage slab using your own quotes — material, delivery, labor and extras itemized, with cost per square foot.

Units

Geometry dimensions — schematic, not to scaleL (length)HW
Schematic · not to scale · quantity repeats the entire solid

Concrete & bag assumptions

Density is the placed concrete density, not dry bag weight. Defaults are examples for normal-weight concrete. Bag weight does not determine yield; use the mixed yield printed on your product.

Estimate cost (optional · USD)

All cost fields are optional and user-entered. Ready-mix and bags are alternatives, never added together. No average or local prices are assumed — use a real quote. Labor per area is available only for shapes with a defined footprint.

Formula & solid model

V = L × W × H × Q

All lengths convert to metres before calculation. Blank waste = 0%. Zero dimensions or quantity produce zero volume. Display values are rounded; costs and bags use unrounded volumes.

Rectangular slab · incl. 10% waste

You need approximately 1.358 cubic yards

36.667 ft³ · 1.038 m³ · 1,038.28 litres

Volume

UnitExact+10% waste
Cubic yards1.2351.358
Cubic feet33.33336.667
Cubic metres0.9441.038
Litres943.8951,038.284

Placed weight · incl. waste

5,500 lb / 2,494.76 kg

Density: 150 lb/ft³ · weight = volume × density

Selected premix bags · incl. waste

62 × 80 lb bags

Yield: 0.6 ft³ / bag · total volume ÷ yield, rounded up.

Above about 1 yd³, ready-mix is often more practical than mixing bags.

Estimate inputs & formula

Length: 10 ft · Width: 10 ft · Thickness (H): 4 in · Quantity (Q): 1

V = L × W × H × Q

Estimate only, not engineering advice. Actual needs vary with subgrade, forms and spillage. Confirm final quantities and product yields with your supplier or contractor before ordering.

What this calculates

This tool combines exact slab geometry with the numbers you supply: your ready-mix or bag price, any delivery or short-load fee, a labor rate per square foot, and a reinforcement/forms allowance.

It reports the material cost, each ancillary cost, the estimated total, and unit costs per square foot and per cubic yard. No average prices are assumed — every dollar figure comes from you.

Formula

Slab volume = L × W × thickness; order quantity = volume × (1 + waste % ÷ 100)

Material = order quantity × your price per yd³

Total = material + delivery + (labor rate × L × W) + extras

Cost per ft² = total ÷ (L × W)

Worked example

10 × 10 ft slab, 4 in thick, at an example $165/yd³ quote

  1. 1.Order quantity: 1.36 cu yd (incl. 10% waste)
  2. 2.Material: 1.36 × $165 ≈ $224
  3. 3.Add a $60 delivery fee and $5/ft² labor (100 ft² = $500): total ≈ $784, or $7.84/ft²

Common mistakes

  • Budgeting only for the concrete itself and forgetting delivery, reinforcement, forms and labor.
  • Using a national average price instead of a current local quote — prices vary widely by region and season.
  • Comparing contractors on total price without checking the slab thickness and reinforcement each quote includes.

Frequently asked questions

How much does a concrete slab cost per square foot?

It depends on thickness, local material prices and labor rates in your area. Enter your own quotes above to get a cost per square foot for your project rather than relying on averages.

Is ready-mix or bagged concrete cheaper for a slab?

Compare a ready-mix quote including delivery with a bag quote using the labelled yield. Choose each material supply in turn; the calculator never adds these alternatives together.