Simple shape formulas
Rectangle = length × width. Triangle = base × perpendicular height ÷ 2. Circle = π × radius². Trapezoid = (parallel side a + parallel side b) × perpendicular height ÷ 2. These are MaterialNest's implemented geometric methods. A triangle's sloping side is not its height; a circle's diameter is twice its entered radius.
L-shaped and irregular surfaces decompose into these simple shapes. Up to 30 included and 30 excluded shapes are supported, with unique names across both lists and positive finite dimensions up to 1,000,000 mm. Rectangle, room and deck/patio modes use rectangular included sections; triangle, circle and trapezoid modes use their named shape. Lot, multiple and irregular modes allow mixed shapes. Changing shape clears incompatible dimensions.
Gross area and exclusions
Gross area = sum of included sections. Excluded area = sum of entered opening/exclusion sections. Net area = gross − excluded; the result must remain positive. No waste or purchase rounding is added. Dimensions alone cannot prove containment or non-overlap; those must be reconciled on a sketch. Use the coordinate-based footprint tool for located geometry checks.
The subtraction checks only the entered area sums: an excluded total at or above gross is rejected. A smaller exclusion outside the footprint can still pass arithmetic validation, as can overlapping included sections. Positive net area therefore does not prove the field sketch is valid. Which area should become a material input depends on the gross versus net decision, not just the arithmetic.
International-foot conversions and display rounding
Net ft² = canonical mm² ÷ 304.8². Square yards = ft² ÷ 9. Square metres = ft² × 0.09290304. Acres = ft² ÷ 43,560. NIST SP 811 Appendix B.9 supplies area conversions; NIST's revised international-foot factors supply the modern acre relationship and identify the obsolete US survey foot. Normal construction calculations use 1 ft = 0.3048 m exactly, never the survey foot.
Version 1.0.0 calculates without intermediate rounding and displays up to four decimal places. Small positive results can display as zero. Saved canonical area preserves calculation precision for explicit Planner handoff. Area does not imply a supported board, paver or sheet layout; use the downstream material calculator's geometry and product rules. Start with the construction measurement guide.