FC

Concrete Calculator

Enter your dimensions and get cubic yards, bag counts, and ready-mix totals in seconds. Built for foundation work, not just a single square slab — save every area and total the whole job.

Concrete Calculator

The live calculator embeds here. Enter your dimensions to get cubic yards, bag counts, and cost in seconds.

Open the Calculator

The basics

How the calculator works

  • 1

    Pick the shape you are pouring

    Slab, footing, wall, column, curb, or stairs. Each shape uses the right volume formula so you are not forcing a footing into a slab calculator.

  • 2

    Enter dimensions in feet and inches

    Type measurements the way you read them off the tape. The calculator converts inches to feet for you before it runs the math.

  • 3

    Add a waste factor

    Default 10% covers spillage, over-excavation, and uneven subgrade. Bump it to 15% for sloppy ground or hand-dug footings.

  • 4

    Save it to the job

    Each area is stored under a named job so a full foundation with footings, walls, and a slab totals up in one place.

Show the math

The formula

Cubic Yards = (L ft × W ft × D ft) ÷ 27

Concrete is ordered in cubic yards, and there are 27 cubic feet in a cubic yard. Convert any inch measurement to feet first (4 inches = 0.333 ft), multiply length × width × depth, then divide by 27. For ready-mix, round up to the nearest quarter yard.

Worked example

A 24 ft × 30 ft garage slab poured at 5 inches thick.

  1. 1.5 in ÷ 12 = 0.417 ft depth
  2. 2.24 × 30 × 0.417 = 300.2 cubic feet
  3. 3.300.2 ÷ 27 = 11.12 cubic yards
  4. 4.11.12 × 1.10 (10% waste) = 12.23 cubic yards

Order 12.25 cubic yards of ready-mix.

20+ years in the field

Real contractor tips

Always order to the quarter yard

Ready-mix plants batch in quarter-yard increments. Round up — running half a yard short on a slab pour will cost you far more than the extra concrete.

Account for the subgrade, not the form

A 4-inch slab over a soft or rutted base can eat 4.5–5 inches of concrete in low spots. Measure your real average depth, not the form height.

Footings always run long

Hand-dug or backhoe footings are never perfectly sized. Add 10–15% on footings specifically — the trench walls bulge and you fill more than the print says.

Know your truck minimums

Most plants charge a short-load fee under 3–4 yards. If you are close, it can be cheaper to bump slab thickness a touch than to eat the small-load surcharge.

Avoid these

Common mistakes contractors make

  • Forgetting to convert inches to feet before dividing by 27.
  • Ordering the exact calculated amount with zero waste factor.
  • Measuring form height instead of average pour depth over the subgrade.
  • Mixing up cubic feet and cubic yards on the order.
  • Calculating each footing separately and losing the running total.
  • Ignoring thickened edges and turn-downs on a monolithic slab.

Versus typical concrete calculators

  • Handles every foundation shape, not just a single rectangular slab.
  • Saves and groups multiple areas under one named job.
  • Applies a contractor waste factor automatically.
  • Gives both ready-mix yardage and bag counts in one view.
  • Remembers your numbers instead of clearing on refresh.

Versus heavy takeoff software

  • No desktop install, license seat, or training required.
  • Runs in the truck or on the slab from your phone.
  • Free to start — no per-project or per-seat pricing.
  • Focused on concrete takeoff instead of a 200-feature suite.
  • Open it and pour today, not after a week of onboarding.

Frequently asked questions

It takes 45 bags of 80 lb concrete, 60 bags of 60 lb, or 90 bags of 40 lb to make one cubic yard. The calculator shows bag counts automatically once you enter dimensions, so you know whether to bag it or call for ready-mix.

Stop guessing yardage on the back of a napkin

Run your next pour through the calculator, save the job, and keep every area in one place. Free to start.

Open the App