Examples
Examples
Try the starting example
- Convex tent outline vertices: x cm, y cm, in boundary order
- 0,0 400,0 400,300 0,300
- Perpendicular inward offset (cm)
- 10
- Groundsheet cut outline vertices (cm)
- (10, 10); (390, 10); (390, 290); (10, 290)
- Inset area (cm²)
- 106400
- Original outline area (cm²)
- 120000
- Cut edge lengths (cm)
- 380, 280, 380, 280
Try another scenario
- Convex tent outline vertices: x cm, y cm, in boundary order
- 0,0 400,0 400,300 0,300
- Perpendicular inward offset (cm)
- 0
- Groundsheet cut outline vertices (cm)
- (0, 0); (400, 0); (400, 300); (0, 300)
- Inset area (cm²)
- 120000
- Original outline area (cm²)
- 120000
- Cut edge lengths (cm)
- 400, 300, 400, 300
Calculation method
Calculation method
Groundsheet cut outline vertices (cm)
Offset each oriented convex boundary line inward by the entered perpendicular distance; intersect neighbouring offset lines. Reject a closed or invalid offset.
Inset area (cm²)
Shoelace area of the computed offset polygon.
Original outline area (cm²)
Shoelace area of the entered convex outline.
Cut edge lengths (cm)
Euclidean distances between consecutive offset vertices, including the closing edge.
Symbols and units
- a
- Convex tent outline vertices: x cm, y cm, in boundary order
- b
- Perpendicular inward offset (cm)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions & limits
Assumptions & limits
- Straight-edged strictly convex polygons only, with measured plan coordinates and a constant perpendicular inset. No seam, hem, corner rounding, material stretch or waterproofing guarantee is added.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.
Further reading
OpenStax: arithmetic and geometry ↗
Background reading; this does not imply endorsement or independent review of SumFizz.