Rectangle Area Calculator
Area, perimeter and diagonal of a rectangle or square.
Results
Area
15
m²
Perimeter
16
m
Diagonal
5.83095
m
What this tool does
The most-used shape in practical life: rooms, walls, plots, sheets of material. The diagonal is included because it is what you measure to check that a frame is square — if both diagonals match, the corners are right angles.
Formula
A = l × w , P = 2 × (l + w)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
l | Length | m |
w | Width | m |
A | Area | m² |
P | Perimeter | m |
D | Diagonal | m |
Worked example
- Length5 m
- Width3 m
- Area15 m²
- Perimeter16 m
- Diagonal5.83095 m
Limitations
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.