Follow a worked example.
Every example below can be loaded using its calculator’s Reset example button. Inputs use centimetres, square centimetres or cubic centimetres as labelled, while angles use degrees.
Equal side and base
Given: Equal side a = 5; Base b = 6.
h = √(a²−b²/4); A = bh/2
| Measurement | Calculated value |
|---|---|
| Equal side | 5 cm |
| Base | 6 cm |
| Height | 4 cm |
| Area | 12 cm² |
| Perimeter | 16 cm |
| Vertex angle | 73.739795° |
Base and height
Given: Base b = 6; Height h = 4.
a = √(h²+b²/4)
| Measurement | Calculated value |
|---|---|
| Equal side | 5 cm |
| Base | 6 cm |
| Height | 4 cm |
| Area | 12 cm² |
| Perimeter | 16 cm |
| Vertex angle | 73.739795° |
Equal side and vertex angle
Given: Equal side a = 5; Vertex angle θ = 60.
b = 2a sin(θ/2)
| Measurement | Calculated value |
|---|---|
| Equal side | 5 cm |
| Base | 5 cm |
| Height | 4.330127 cm |
| Area | 10.825318 cm² |
| Perimeter | 15 cm |
| Vertex angle | 60° |
Perimeter and base
Given: Perimeter P = 16; Base b = 6.
a = (P−b)/2; P > 2b
| Measurement | Calculated value |
|---|---|
| Equal side | 5 cm |
| Base | 6 cm |
| Height | 4 cm |
| Area | 12 cm² |
| Perimeter | 16 cm |
| Vertex angle | 73.739795° |
Check the answer’s dimensions
An area contains a product of two lengths, while volume contains three. A perimeter or radius is still a length. If your input measurements are mixed between metres and centimetres, convert them to a common unit first. A realistic-looking number can still be wrong if the units were inconsistent.