Concrete Takeoff: Cubic Yards, Rebar and Formwork With Worked Examples

A concrete takeoff turns structural drawings into three kinds of quantities: the volume of concrete in cubic yards, the weight of reinforcing steel and the area or length of formwork. Because concrete is bought by the cubic yard but placed, formed and finished in many other units, a complete takeoff keeps each item separate and traceable. This guide shows how to measure the common elements, with simple arithmetic examples you can check yourself.

Where to find concrete information

Concrete work is mainly Division 03 in CSI MasterFormat. The structural drawings (sheets prefixed S) show footings, slabs, walls, columns, beams and elevated decks; the foundation plan, sections and details give dimensions and reinforcing; general notes give concrete strengths, cover and lap lengths. The specifications cover mix requirements, formwork, reinforcing, placing, finishing, curing and testing. Also read the civil sheets for slabs on grade, curbs and paving, and the architectural sheets for stairs, equipment pads and openings.

Unit conversions you will use every day

• 1 cubic yard = 27 cubic feet.
• Thickness in inches divided by 12 gives feet (6 inches = 0.5 feet).
• Volume in cubic feet divided by 27 gives cubic yards.

Example 1: slab on grade

A slab measures 40 feet by 30 feet and is 6 inches thick. Area is 40 x 30 = 1,200 square feet. Volume is 1,200 x 0.5 = 600 cubic feet, which is 600 / 27 = 22.2 cubic yards. Add a waste or over-excavation allowance (5 percent is used here only as an example): 22.2 x 1.05 = 23.3 cubic yards. Then take off the other slab items separately: formwork at the slab edge (140 linear feet), vapor barrier and base area (1,200 square feet), control joints, reinforcing and the finishing area.

Example 2: continuous footing

A continuous footing runs 100 feet, is 2 feet wide and 1 foot deep. Volume is 100 x 2 x 1 = 200 cubic feet, or 200 / 27 = 7.4 cubic yards. Footings usually need side forms unless they are poured against earth, so check the details: if both sides are formed, the formwork area is 100 x 1 x 2 = 200 square feet of contact area. Excavation and backfill belong in the earthwork takeoff (Division 31).

Example 3: foundation wall

A wall is 100 feet long, 8 feet high and 8 inches thick. Volume is 100 x 8 x (8 / 12) = 533 cubic feet, or 19.8 cubic yards. Formwork contact area is both faces: 100 x 8 x 2 = 1,600 square feet. Subtract openings larger than the threshold in your practice, and add pilasters, corners and wall thickenings from the details.

Reinforcing steel takeoff

Reinforcing is measured in linear feet by bar size, converted to weight and priced per pound or ton. Bar weight per foot is standard: a #4 bar weighs 0.668 pounds per foot. For the 40 by 30 foot slab with #4 bars at 12 inches on center each way, count the bars in each direction: 41 bars of 30 feet (1,230 feet) and 31 bars of 40 feet (1,240 feet), a total of 2,470 feet. At 0.668 pounds per foot that is about 1,650 pounds before laps, chairs and waste. Check the structural notes for lap lengths, cover, bends, hooks and dowels, and add the accessories (chairs, tie wire, spacers).

Example 4: a rectangular column

A column is 16 inches by 16 inches and 12 feet tall. Convert the section to feet: 16 / 12 = 1.333 feet each way. Volume is 1.333 x 1.333 x 12 = 21.3 cubic feet, or 21.3 / 27 = 0.79 cubic yards. The formwork contact area is the perimeter times the height: 4 x 1.333 x 12 = 64 square feet. Vertical bars and ties come from the column schedule, which gives the bar count, size and tie spacing. Because columns are repeated, count the number of each type from the plans and multiply, then add the footing, pier and any dowels that belong to each column.

Elevated slabs, beams and decks

Elevated concrete is measured by element: slab area and thickness, beam length and cross-section below the slab, drop panels and capitals, plus edge forms and openings. Shoring and reshoring are major cost items, so measure the supported area and the height. For slabs on metal deck, volume depends on the deck profile, so use the manufacturer's volume per square foot or the structural notes rather than the nominal thickness alone.

A short concrete takeoff checklist

1. Confirm the drawing revision and read all structural notes and details.
2. Take off concrete by element (footings, walls, slabs, columns, beams) with the mix strength for each.
3. Take off reinforcing by bar size and element, with laps, dowels and accessories.
4. Take off formwork contact area and edge forms, shoring and stripping.
5. Add finishing, curing, joints, embeds and testing as the specifications require.
6. Show waste and ordering allowances as separate lines.
7. Have a second person check dimensions and counts against the marked-up plans.

Formwork

Formwork is measured as contact area (square feet of surface touched by concrete) and sometimes as linear feet for edge forms. Classify it by element, because walls, columns, beams, elevated slabs and footings have different labor and reuse patterns. Include shoring and reshoring for elevated work, stripping, cleaning and repairs. Pricing may use units such as cost per square foot of contact area, and the number of reuses has a large effect on cost.

Placing, finishing and the extras

• Pumping or conveying, depending on access.
• Finishing: float, trowel, broom or other finishes per specification, measured in square feet.
• Curing, sealers and hardeners where specified.
• Embedded items, anchor bolts, sleeves, joints, waterstop and inserts.
• Testing and inspection (cylinders, slump), if they are in your scope.
• Cold or hot weather protection, which depends on the season and location.

Waste, overage and ordering

Ready-mix suppliers deliver in truckloads, and small over-orders are normal because forms, subgrade and spillage vary. The percentage to add depends on the element and your experience, so show net volume, the allowance and the order quantity as separate lines. For small pours, check the supplier's minimum load and short-load charges.

Common concrete takeoff mistakes

• Measuring from architectural dimensions that differ from the structural drawings.
• Forgetting thickened slab edges, haunches, pilasters or pits in the foundation plan.
• Missing reinforcing at corners, openings and dowels between pours.
• Pricing only the concrete and missing formwork, finishing or curing.
• Using outdated drawings after an addendum.

How Bid Sharp helps

Bid Sharp prepares concrete takeoffs and estimates covering volume, reinforcing, formwork and finishing, with quantities traceable to marked-up structural sheets. See concrete estimating, quantity takeoff and our free calculators, or send us your plans and bid date.