FixerCalc

Concrete Calculator

Concrete is sold by the cubic yard. This calculator turns a pad’s length, width, and thickness into yards and an equivalent bag count so you can choose ready-mix vs. mixing on the driveway.

Last reviewed 2026-08-25. How we calculate

Results update as you type. Units stay imperial inside the math.

Slab
Bags
Pricing

Results

  • Cubic yards

    1.33

  • 80 lb bags

    60

  • 60 lb bags

    80

  • Cubic feet

    36.0

  • Ready-mix material (your $/yd)

    $233.33

Net yards before waste
1.23
  • Shorting a ready-mix order is expensive. Round yards up the way your dispatcher asks (often to 0.5 yd³).
  • This is volume only—not mix design, rebar, fiber, base rock, or finishing.

How this calculation works

  1. Volume in cubic feet is length × width × thickness in feet (inches ÷ 12).
  2. Cubic yards divide by 27. Waste covers over-excavation and spillage—not a license to skip a compact base.
  3. Bag counts divide cubic feet by the yield printed on the bag (defaults are common Type S/N bagged mix yields).

ft³ = L × W × (t_in/12) × (1+waste%); yd³ = ft³/27; bags = ceil(ft³ / bag yield)

What to do next

  • For anything bigger than a few bags, ready-mix is usually more consistent. Ask about short-load fees.
  • Confirm thickness with the use: sidewalks ~4 in; many residential drives 4–6 in over base.
  • Plan control joints and reinforcement with someone who will warranty the slab.

FAQ

How many 80-pound bags in a yard?
At 0.60 cubic feet per bag, 27 ÷ 0.60 = 45 bags per yard before waste. Always round up, and verify yield on your bag.
Should I order 1.2 or 1.5 yards if I calculate 1.23?
Talk to the plant. Many will not dispatch odd hundredths, and you cannot send the truck back for 0.1 yard cheaply. Rounding up is normal.

Sources

  • yd³ = length × width × (thickness in / 12) / 27
  • Typical bag yields: 80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³ (check the bag; mixes vary)

Cost defaults are typical US planning bands, last reviewed 2026-08-25. Edit the price fields on this page rather than treating them as a local market index.