ProjectCalc (working name)

Concrete Calculator

Cubic yards for ready-mix, or exact bag counts if you're mixing it yourself — for slabs, footings and post holes.

Feet — fractions welcome
Feet (footing: trench width, e.g. 1.5)
Inches — 4″ is standard for slabs and footings
Uneven grade eats concrete — 10% is the pros' habit
Typically $140–$190/yd³ + short-load fees under ~5 yd³

MeasureAmount
Cubic yards (ready-mix)
80-lb bags (0.60 cu ft each)
60-lb bags (0.45 cu ft each)
40-lb bags (0.30 cu ft each)

Bag math: above ~1 cubic yard, mixing bags by hand is a very long day — ready-mix usually wins on cost and sanity. Most plants have a minimum order and short-load fees.

🛒 Shopping list

ItemQty
Concrete
Welded wire mesh 5′ × 150′ roll (or rebar grid)
Form boards, stakes & screws
Gravel base (4″, compacted) — via our gravel calculatorCalculate →

✅ Project checklist

  • Excavate, then compact a 4″ gravel base; forms level, braced, and oiled
  • Mesh/rebar on chairs — never on the ground, never hooked up mid-pour
  • Book the truck for the coolest part of the morning; crew and tools ready before it arrives
  • Screed, bull-float, edge and joint; cut control joints within 6–12 hours
  • Keep it moist/covered for 7 days of curing — no vehicles for a week

How the math works

Slabs and footings: volume = length × width × thickness. Post holes: π × (diameter ÷ 2)² × depth × number of holes. Cubic yards = cubic feet ÷ 27. Bag counts use the standard yields printed on the bags: an 80-lb bag makes 0.60 cu ft of concrete, a 60-lb bag 0.45, a 40-lb bag 0.30.

For estimation only. Confirm mix design and minimum-order terms with your ready-mix plant or supplier.