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.
Length and width
Given: Length a = 8; Width b = 5.
A = ab; P = 2(a+b); d = √(a²+b²)
| Measurement | Calculated value |
|---|---|
| Length | 8 cm |
| Width | 5 cm |
| Area | 40 cm² |
| Perimeter | 26 cm |
| Diagonal | 9.4339811 cm |
Diagonal and one side
Given: Diagonal d = 10; Known side a = 6.
b = √(d²−a²)
| Measurement | Calculated value |
|---|---|
| Length | 6 cm |
| Width | 8 cm |
| Area | 48 cm² |
| Perimeter | 28 cm |
| Diagonal | 10 cm |
Area and one side
Given: Area A = 40; Known side a = 8.
b = A/a
| Measurement | Calculated value |
|---|---|
| Length | 8 cm |
| Width | 5 cm |
| Area | 40 cm² |
| Perimeter | 26 cm |
| Diagonal | 9.4339811 cm |
Perimeter and one side
Given: Perimeter P = 26; Known side a = 8.
b = P/2−a
| Measurement | Calculated value |
|---|---|
| Length | 8 cm |
| Width | 5 cm |
| Area | 40 cm² |
| Perimeter | 26 cm |
| Diagonal | 9.4339811 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.