Reviewed by CalcMulti Editorial Team·Last updated: ·← Geometry Hub
The area of a rectangle is found by multiplying its length by its width: A = l × w. This formula works for any rectangle — a square is a special rectangle where l = w. The result is in square units (cm², m², in², ft², etc.).
The perimeter is the total distance around the rectangle: P = 2(l + w). The diagonal — the straight line from one corner to the opposite corner — is found using the Pythagorean theorem: d = √(l² + w²). This calculator computes all three from just two inputs.
A = l × w
| Length | Width | Area | Perimeter | Diagonal |
|---|---|---|---|---|
| 3 | 4 | 12 | 14 | 5.00 |
| 5 | 12 | 60 | 34 | 13.00 |
| 6 | 8 | 48 | 28 | 10.00 |
| 8 | 15 | 120 | 46 | 17.00 |
| 10 | 6 | 60 | 32 | 11.66 |
| 12 | 5 | 60 | 34 | 13.00 |
| 15 | 10 | 150 | 50 | 18.03 |
| 20 | 15 | 300 | 70 | 25.00 |
A = s² — area, perimeter, and diagonal of a square
Triangle Area Calculator½bh, Heron's formula, or SAS method
Trapezoid Area Calculator½(a+b)×h — two parallel sides and height
Perimeter CalculatorPerimeter of rectangles, triangles, circles, polygons
Circle Area CalculatorA = πr² from radius, diameter, or circumference
Surface Area Calculator3D shapes — cube, cylinder, sphere, cone
This calculator is for educational purposes only and does not constitute professional advice. Results are based on standard mathematical formulas. Always verify critical calculations with a qualified professional before making important decisions.