Choose the method that matches the information available
Quick Shapes uses defined geometric formulae, so its area is exact for the entered shape and dimensions. The three-sided triangle uses Heron’s formula and validates the triangle inequality. The trapezoid option assumes the two non-parallel sides are equal; split an asymmetric shape or use another mode.
Sketch Estimate keeps the angles and proportions of the phone drawing. One measured edge sets the scale. With several measured edges, a least-squares scale is fitted and each residual is reported. The polygon is not distorted to force agreement, because the side lengths alone cannot solve its angles.
Dimensioned Polygon splits a convex polygon into measured triangles from one anchor. A polygon with n vertices requires every boundary side and n − 3 internal diagonals. Each triangle must satisfy the triangle inequality before its Heron area contributes to the total.
sketch estimate: scaled area = drawn area × best-fit scale²
dimensioned polygon: total area = Σ Heron triangle areas
material volume = area × uniform depth × number of areas
Worked example
A 12 m by 8 m rectangle has an exact plan area of 96 m² and a perimeter of 40 m. At 150 mm uniform depth the net volume is 14.4 m³. With a 10% ordering allowance, the order volume is 15.84 m³. At the editable Type 1 starting density of 2,200 kg/m³, that is 34,848 kg or 34.848 metric tonnes. Two full 16-tonne payloads would leave a final partial quantity of 2.848 tonnes.
Material assumptions
The Type 1, 6F2, asphalt, concrete, gravel, sand and topsoil values are editable starting points, not supplier-certified densities. Moisture, grading, source, voids and compaction change bulk density. Keep the selected loose, placed or compacted basis consistent with the depth being quantified.
Frequently asked questions
Can I calculate a general polygon from side lengths alone?
No. Many polygons can share the same side lengths but have different angles and areas. Use the sketch mode for a clearly labelled estimate, or measure enough internal diagonals to create fully constrained triangles.
Why are residuals shown for measured sketch edges?
Residuals show how far each fitted sketch edge differs from its entered measurement. A large residual means the sketch proportions disagree with the measured lengths, so the drawing should be adjusted or the measurements checked.
Can I use a concave footprint?
Use quick or sketch mode for an estimate, or split the footprint into convex additive and subtractive zones for dimensioned work. Record the split clearly in the field report.