Construction unit converter

The conversions estimators use daily

Construction pricing mixes units on purpose: materials sell in the unit their supplier ships, labor prices in the unit a crew produces, and drawings dimension everything in feet and inches. The converter above handles the four families that show up in nearly every takeoff.

Area: sf to sy and squares. Divide square feet by 9 for square yards (carpet, some flatwork) and by 100 for roofing squares. 1,800 sf of carpet is 1,800 / 9 = 200 sy; a 2,400 sf roof is 24 squares.

Volume: cf to cy. Divide cubic feet by 27. A 750 cf slab is 27.8 cy. The single most common conversion error in new estimators' math is dividing by 9 here; 9 converts area, 27 converts volume.

Board feet. Nominal thickness (in) x nominal width (in) x length (ft) / 12, per piece. Forty 2x10x16 joists run 2 x 10 x 16 / 12 = 26.67 bf each, 1,067 bf total. Lumber quotes price per MBF, a thousand board feet.

Wall length to sheets. Length (lf) x height (ft) gives one face in sf; double it for both faces of a partition; divide by sheet area (48 sf for a 4x12, 32 sf for a 4x8) and round up. 240 lf at 9 ft, both faces, is 4,320 sf and 90 sheets of 4x12 before waste.

Why unit discipline protects margin

Unit mistakes are silent: the math runs, the spreadsheet fills, and the number is simply wrong by a factor of 3 or 9 or 27. The professional habit is to write the unit next to every quantity and price (240 lf, $2.40 per sf) and let the units cancel like algebra. If the units do not cancel to dollars, the line is broken no matter what the calculator says.

Ruh applies the same discipline automatically: its takeoff carries the unit on every measured quantity from your drawings and prices each line against the matching unit rate in your own price book, with your estimator reviewing before anything goes in a bid. The glossary covers each unit in depth: sq, sy, cy, bf, and lf, and the full workflow lives in how to estimate construction costs.