Triangle from Three Sides calculator.
Find area and perimeter when you can measure three edges but cannot measure a perpendicular height.
Your inputs
Use measurements from your plan and properties from your chosen product. Any prefilled values are illustrative.
A clear estimate starts here.
Enter your dimensions and product details to see the quantity and purchase breakdown.
Formula and assumptions
How this calculation works.
Heron’s formula requires a non-degenerate triangle. This differs from entering a known perpendicular height.
A worked example
Illustrative inputs only. Product properties and design dimensions are not recommendations for your project.
- First edge
- 3 m
- Second edge
- 4 m
- Third edge
- 5 m
Triangle area: 6 m²
Before you purchase
Use dimensions from your plan and properties from your chosen product. Any design spacing, section or fixing pattern must already be specified.
Heron’s formula requires a non-degenerate triangle. This differs from entering a known perpendicular height.
Method: dimensional arithmetic and user-supplied specifications. Software checks: 2026-10-04. Calculation and review policy.