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.
From the side
Given: Side a = 6.
A = √3 a²/4; h = √3 a/2
| Measurement | Calculated value |
|---|---|
| Side | 6 cm |
| Area | 15.588457 cm² |
| Perimeter | 18 cm |
| Altitude | 5.1961524 cm |
| Inradius | 1.7320508 cm |
From area
Given: Area A = 15.5884572681.
a = √(4A/√3)
| Measurement | Calculated value |
|---|---|
| Side | 6 cm |
| Area | 15.588457 cm² |
| Perimeter | 18 cm |
| Altitude | 5.1961524 cm |
| Inradius | 1.7320508 cm |
From the altitude
Given: Altitude h = 5.
a = 2h/√3
| Measurement | Calculated value |
|---|---|
| Side | 5.7735027 cm |
| Area | 14.433757 cm² |
| Perimeter | 17.320508 cm |
| Altitude | 5 cm |
| Inradius | 1.6666667 cm |
From the perimeter
Given: Perimeter P = 18.
a = P/3
| Measurement | Calculated value |
|---|---|
| Side | 6 cm |
| Area | 15.588457 cm² |
| Perimeter | 18 cm |
| Altitude | 5.1961524 cm |
| Inradius | 1.7320508 cm |
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.