Rectangle Area Calculator
Calculate the area, perimeter, and diagonal of any rectangle instantly. Enter the length and width for step-by-step solutions.
What is the Area of a Rectangle?
The area of a rectangle is the amount of space enclosed within its four sides. It's calculated by multiplying the length by the width (A = l ร w). Rectangles are everywhereโfrom rooms and screens to books and doors. Understanding rectangle area is essential for construction, interior design, landscaping, and countless real-world applications.
Area Formula
A = l ร wMultiply the length by the width to get the area in square units.
Perimeter Formula
P = 2(l + w)Add length and width, then multiply by 2 to get the total distance around.
Diagonal Formula
d = โ(lยฒ + wยฒ)Use the Pythagorean theorem to find the diagonal length.
Area from Diagonal & Side
A = l ร โ(dยฒ - lยฒ)If you know the diagonal and one side, you can still find the area.
Examples
Room Floor Area: 12ft ร 10ft
A = 12 ร 10 = 120 square feet. Perfect for calculating flooring or carpet. = 120 sq ft
TV Screen: 55" diagonal, 16:9 ratio
Width โ 47.9", Height โ 26.9". Area = 47.9 ร 26.9 โ 1289 sq inches. = โ 1289 sq in
Garden Bed: 8m ร 1.5m
A = 8 ร 1.5 = 12 square meters. P = 2(8 + 1.5) = 19m for fencing. = 12 mยฒ, 19m perimeter
Notebook Page: 21cm ร 14.8cm (A5)
A = 21 ร 14.8 = 310.8 cmยฒ or about 0.031 mยฒ. = 310.8 cmยฒ
Frequently Asked Questions
What is the formula for area of a rectangle?
The area of a rectangle is calculated using A = length ร width. For example, a rectangle with length 8 cm and width 5 cm has an area of 40 cmยฒ.
How do I find the perimeter of a rectangle?
The perimeter is the total distance around the rectangle: P = 2(l + w). For a 10m ร 6m rectangle, P = 2(10 + 6) = 32 meters.
What is the difference between area and perimeter?
Area measures the space inside (in square units), while perimeter measures the distance around the edge (in linear units). Area fills the shape; perimeter traces its boundary.
How do I calculate the diagonal of a rectangle?
Use the Pythagorean theorem: d = โ(lยฒ + wยฒ). A rectangle with sides 3 and 4 has diagonal = โ(9 + 16) = โ25 = 5.
Is a square a rectangle?
Yes! A square is a special rectangle where all sides are equal. The area formula still works: A = sยฒ (since l = w = s).