Concrete estimator

What a concrete estimator does

A concrete estimator turns a slab's dimensions into a dollar figure: how many cubic yards you will order and what the ready-mix, waste, and pump add up to. It answers the pricing question, not the quantity question. The quantities (cubic yards and bag counts for every shape, from slabs to footings to columns) live on the concrete calculator. This page takes those yards and prices them at a ready-mix rate you control. Use the calculator to get the volume, use this estimator to plan the spend.

The cost formula

Volume comes first: cubic yards = length (ft) x width (ft) x (thickness in inches / 12) / 27, because a cubic yard is 27 cubic feet. Then you add waste and price the result. Worked example, a 20 x 20 slab at 4 inches: 400 square feet x 0.333 ft = 133.3 cubic feet, / 27 = 4.94 CY. Add 5 percent waste and you order 5.19 CY. At $165 per cubic yard that is about $855.56 of ready-mix, which works out to $2.14 per square foot. That per-SF figure is material only. It does not include the crew, forms, finishing, or a pump.

Ready-mix pricing and short-load fees

Ready-mix runs roughly $150 to $180 per cubic yard delivered, and that range is a planning figure, not a quote: it swings with your market, the mix design (PSI strength, fiber, air entrainment), and fuel. Always price against a real supplier number when you have one. The other line that surprises people is the short-load fee. Plants load a full truck at about 10 CY, and when your pour is under roughly 4 CY they add a per-yard short-load charge to cover the trip. A small stoop or pad can carry a fee that rivals the concrete itself, so on tiny pours confirm minimum-load terms before you book.

When you need a concrete pump

A pump is about access, not volume. If the truck chute cannot reach the forms (a backyard slab behind a house, an elevated deck, a long carry over soft ground, or anything the mixer cannot back up to) you rent a pump. A pump day is a flat mobilization cost, typically $900 to $1,200, and it does not scale with the yardage, which is why this estimator keeps it out of the per-square-foot rate. Line-pump versus boom-pump and travel distance move the number, so treat the default as a placeholder and drop in your local rate.

Slab thickness and related figures

Thickness drives both volume and cost, so it is the first number to get right. Four inches is the standard for patios, walkways, and residential floors. Driveways and anything carrying vehicle loads go to 5 or 6 inches, and heavy equipment or thickened edges go deeper still. Every extra inch on a 400 SF slab is another 1.2 CY of concrete, so thickness is not a rounding decision. Waste of 5 percent covers a clean, well-formed pour on flat subgrade; bump it to 10 percent for rough grade, spillage, or complex forms where over-excavation and edge loss eat into the order.

From cubic yards to a priced bid

A slab total is one number on a job that has many. The full estimate has to fold in rebar or mesh, vapor barrier, forms, the finishing crew, and every other assembly on the drawings, and that takeoff is where bids are won or lost. Ruh reads your plan set, quantifies the concrete and everything around it, and drafts a priced estimate against your own cost book, so the ready-mix line is traceable back to the sheet it came from. See how it works on the concrete estimating software page.