Concrete Formwork Material Estimator

How it works

Contact area: wall/footing = 2 × L × H, column = n × 2(W + D) × H, edge = L × H; plywood = area × 1.10 ÷ 32 ft² ÷ reuses; lateral pressure (ACI 347, walls) p = 150 + 9,000 R/T psf, 600 ≤ p ≤ 150 h; tie spacing = √(tie capacity ÷ p)

Formwork is estimated by contact area — every square foot of concrete surface that has to be held in shape — which for a wall is both faces, for a column all four, and for a footing the two sides. Plywood covers that area with a waste allowance and is amortised over the number of pours a sheet survives (three to five for plain ply, ten or more for overlaid panels), while studs, walers and braces scale roughly with the area. Fresh concrete pushes outward like a fluid, and the pressure at the base grows with how fast the wall is filled and how cold it is (ACI 347’s rate-and-temperature formula), which sets how closely the ties that hold the two faces together must be spaced. Labour dominates formwork cost — typically 0.05–0.18 crew-hours per square foot to erect, align and strip — so reusable gang forms and simpler geometry pay off quickly.

Worked example

An 80 ft wall 8 ft high has 1,280 ft² of contact area. With four reuses and 10% waste that is 11 sheets of ¾″ form ply, about 1,280 lf of studs plus 640 lf of walers, 160 snap ties on a 2 ft grid (a 4 ft/h pour gives 664 psf, so 3,000 lb ties can be up to 2.1 ft apart), 3.2 gal of release oil per pour and roughly 128 crew-hours — four days for a four-person crew.

Frequently asked questions