Case 1
- Length
- 4
- Width
- 3
12.00
Open with these valuesRectangle Area Calculator
12.00units²
Result: 12.00 units²Length times width, and nothing more: a 4 by 3 rectangle covers 12 square units. The perimeter 2(L+W) is 14 and the diagonal √(L²+W²) is 5 — the classic 3-4-5 triangle. A square is only a rectangle whose two sides happen to be equal.
The numbers at a glance
Held fixed: Length 4.000.
| Width | Result |
|---|---|
| 1.000 | 4.00 |
| 2.000 | 8.00 |
| 3.000Your value | 12.00 |
| 4.000 | 16.00 |
| 5.000 | 20.00 |
| 6.000 | 24.00 |
Worked examples
Case 2
- Length
- 5
- Width
- 5
25.00
Open with these valuesCase 3
- Length
- 6
- Width
- 8
48.00
Open with these valuesHow it's calculated
A = L × W
- StepMeasure the two sides that meet at a corner, both in the same unit.
- StepEnter the longer side as the length and the shorter as the width.
- ResultRead the area in the square of that unit.
Reference table
| Length, width | Perimeter, diagonal | Area |
|---|---|---|
| 1.5, 4 | 11 and 4.272002 | 6 |
| 4, 3 | 14 and 5 | 12 |
| 10, 2 | 24 and 10.198039 | 20 |
| 5, 5 | 20 and 7.071068 | 25 |
| 6, 8 | 28 and 10 | 48 |
Questions
How do I calculate the area of a rectangle?
Multiply the length by the width. A rectangle 4 long and 3 wide covers 4 × 3 = 12 square units. Both sides must be in the same unit, and the area comes back in square units of it.
What is the difference between area and perimeter?
The area is the surface inside the rectangle — what you cover with paint, flooring or fabric. The perimeter is the border length around the outside, found with 2 × (L + W). For a 4 by 3 rectangle the area is 12 and the perimeter is 14.
How do I find the diagonal of a rectangle?
With the Pythagorean theorem, diagonal = √(L² + W²). For a 4 by 3 rectangle that is √25 = 5, the classic 3-4-5 right triangle. The diagonal is always longer than either side.
Is a square a rectangle?
Yes — a square is a rectangle with equal sides. Enter the same value twice and a 5 by 5 square gives an area of 25, a perimeter of 20 and a diagonal of about 7.071068.
What units does the rectangle calculator use?
Any length unit, as long as both sides share it. Centimetres in, square centimetres out; inches in, square inches out.
Sources and last check
Information, not professional advice.