Unit Conversions for Construction & Building

Feet and Inches to Meters for Blueprints

Construction in the United States is built on feet and inches, while international projects and an increasing number of domestic specifications use metric units. The fundamental conversion is 1 foot = 0.3048 meters exactly, and 1 inch = 25.4 mm exactly. When reading metric blueprints, dimensions are typically given in millimeters, even for large measurements — a 3.6-meter wall appears as 3,600 mm. Use our length converter to translate between systems quickly and avoid costly measurement errors on site.

Square Footage to Square Meters

Area calculations for flooring, painting, tiling, and insulation require converting between square feet and square meters. The conversion factor is 1 square foot = 0.0929 square meters, or equivalently, 1 square meter = 10.764 square feet. When ordering materials from international suppliers or working on projects with metric specifications, a reliable area converter prevents expensive under- or over-ordering. For a deeper dive into this conversion, see our square feet to square meters guide.

Cubic Yards to Cubic Meters for Concrete and Soil

Concrete, gravel, soil, and mulch are ordered by volume. In the US, the standard unit is the cubic yard (27 cubic feet). Metric countries use cubic meters. The conversion is 1 cubic yard = 0.7646 cubic meters. When estimating concrete for a foundation, calculate length × width × depth in consistent units, then convert. For example, a slab 20 ft × 30 ft × 4 inches thick equals (20 × 30 × 0.333) / 27 = 7.4 cubic yards, or approximately 5.7 cubic meters. Always order 5-10% extra to account for waste and spillage.

Board Feet for Lumber

Lumber in North America is sold by the board foot — a unit unique to the timber industry. One board foot equals a piece of wood 12 inches long, 12 inches wide, and 1 inch thick (144 cubic inches, or 2,360 cm³). To calculate board feet: (thickness in inches × width in inches × length in feet) / 12. A 2×6 board that is 8 feet long contains (2 × 6 × 8) / 12 = 8 board feet. Metric lumber is sold by the cubic meter, so converting between the systems requires knowing that 1 board foot = 0.002360 m³, or about 424 board feet per cubic meter.

Roof Pitch and Angle Conversions

Roof pitch in the US is expressed as a ratio of rise to run, typically stated as “X in 12” — for example, a 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. To convert pitch to degrees, use the arctangent function: angle = arctan(rise / run). A 6:12 pitch equals arctan(6/12) = 26.57°. Common conversions include 4:12 = 18.4°, 6:12 = 26.6°, 8:12 = 33.7°, and 12:12 = 45°. International specifications often state roof slope in degrees or as a percentage.

Pipe Sizing: Imperial vs Metric

Pipe sizing is notoriously confusing because “nominal pipe size” (NPS) in the US does not correspond to any actual dimension of the pipe. NPS 1 is not 1 inch in outside diameter — it is 1.315 inches. The metric equivalent, DN (Diamètre Nominal), uses millimeters but is similarly nominal. Common equivalences include NPS 1/2 = DN 15, NPS 1 = DN 25, NPS 2 = DN 50, and NPS 4 = DN 100. When sourcing fittings internationally, always verify both the nominal size and the actual dimensions to ensure compatibility.

Rebar Sizing Conversions

Reinforcing steel bars in the US are designated by numbers representing eighths of an inch in diameter. A #4 bar is 4/8 inch (12.7 mm) in diameter. Metric rebar is designated by its diameter in millimeters. Common equivalences include #3 = 10 mm, #4 = 13 mm, #5 = 16 mm, #6 = 19 mm, and #8 = 25 mm. These are approximate — metric and imperial rebar are not perfectly interchangeable, so structural calculations must use the actual cross-sectional area for the specific bar being used.

Material Coverage Rates

• Paint: 1 gallon covers ~350–400 sq ft (32–37 m²)
• Concrete: 1 cubic yard covers 81 sq ft at 4 inches thick (1 m³ covers ~10 m² at 100 mm)
• Mulch: 1 cubic yard covers ~100 sq ft at 3 inches deep (1 m³ covers ~13 m² at 75 mm)
• Gravel: 1 ton covers ~50–80 sq ft at 2 inches deep, depending on stone size

Tips for International Specifications

When working with international blueprints or sourcing materials from overseas, always confirm the unit system at the outset. Establish a single system for all on-site measurements and convert all supplier specifications to match. Use our length, area, and volume converters to verify every conversion before cutting, pouring, or ordering. In construction, measure twice and convert carefully — the cost of a mistake is always higher than the cost of double-checking.