Foot One engine, consistent results
All calculator pages use the same pure calculation functions. Guides and reference tables compute worked examples from that engine at build time. Arithmetic uses JavaScript double-precision numbers; results are rounded only for display.
Conversion constants
| Unit | Definition used |
|---|---|
| Foot | 0.3048 meters exactly; 12 inches |
| Square yard | 9 square feet exactly |
| Square meter | 1 ÷ 0.3048² ≈ 10.7639104167 sq ft |
| Acre | 43,560 sq ft = 4,046.8564224 m² |
| Hectare | 10,000 m² ≈ 2.4710538147 acres |
| Cubic yard | 27 cubic feet exactly |
Sources: NIST revised unit conversion factors and NIST Handbook 44, Appendix C. We use the international foot. The U.S. survey foot was retired for new work on January 1, 2023; legacy survey data may need explicit conversion. See NIST’s U.S. survey foot guidance.
Area formulas
- Rectangle: length × width.
- L-shape: outer length × outer width − cutout length × cutout width.
- Circle: π × radius².
- Triangle: base × perpendicular height ÷ 2.
- Trapezoid: (parallel side A + parallel side B) × perpendicular height ÷ 2.
- Ordered polygon points: ½ × |Σ(xᵢyᵢ₊₁ − xᵢ₊₁yᵢ)|, closing the last point back to the first. This is the shoelace formula. Crossing or touching nonadjacent edges and zero-area polygons are rejected.
Map area and perimeter
Turf area computes spherical geodesic area in square meters from longitude/latitude coordinates. Turf length computes the perimeter of the closed boundary using great-circle distances. Turf uses a mean Earth radius of 6,371,008.8 meters. These are horizontal spherical estimates, not ellipsoidal survey calculations or sloped surface areas. Drawings are limited to 200 corners and cannot cross the date line.
Map display: Leaflet, with © OpenStreetMap contributors. Public tiles are subject to OpenStreetMap’s tile usage policy; availability is not guaranteed.
Quantities and cost
Net area = included areas − excluded areas. Order area = net × (1 + waste percentage ÷ 100). Boxes = order area ÷ coverage per box, rounded up. Estimated material cost = order area × price per sq ft. Volume = square feet × depth in feet; divide an inch depth by 12 first. Unit price = total price ÷ area.
Results are estimates. The map, listing measurements and material coverage each have limits beyond the arithmetic. Sources reviewed November 8, 2026.