Rectangle Area Calculator

Fast, accurate and free online rectangle area calculator tool running directly in your browser.

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Area of a rectangle = a · b — product of adjacent side lengths. Enter the lengths of sides a and b.

Unit:

Side a

Side b

Area rectangle

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The formula for the area of a rectangle and its meaning in practice

The area calculator of a rectangle is an irreplaceable and one of the simplest online mathematical tools for quickly determining the area of quadrilaterals with four right angles. In everyday life, construction, architecture and finishing works, the rectangular shape is ubiquitous. Floors in rooms, walls, window panes, table tops, TV screens, as well as entire building plots are most often rectangular in shape.

Precise calculation of the area of the rectangle allows you to accurately plan costs and purchases. Regardless of whether you plan to lay floor panels, paint the walls, buy the appropriate amount of carpet, or estimate the fertilizer consumption for flower beds - our rectangle area calculator will perform these calculations in a fraction of a second, eliminating the risk of calculation errors.

How to calculate the area of a rectangle? The basic formula

The area of a rectangle is the product of the lengths of its two adjacent sides. Since the opposite sides of the rectangle are equal and parallel, and all interior angles are 90 degrees, the mathematical formula is:

P = a × b

Where each symbol means:

P:The area of the rectangle expressed in square units.
a:Length of the first side (e.g. width).
b:Length of the other side (e.g. length).

Conversions of rectangular areas in various industries

Example object	Length of side A (a)	Length of side B (b)	Surface area (P)	Application of the result in practice
Living room	4.5 m	3.2 m	14.4 m²	Determination of the area for laying panels and purchasing skirting boards.
Kitchen wall	2.8 m	2.5 m	7.0 m²	Determination of the number of ceramic tiles or the efficiency of wall paint.
Recreational plot	50 m	20 m	1000 m² (10 ares)	Planning of space development, fencing and plantings.
A4 paper sheet	297 mm	210 mm	62370 mm² (0.062 m²)	Graphic design, printing and packaging of shipments.

Step by step: how to calculate the area of a rectangle? Examples

Let's analyze two simple, everyday scenarios in which calculating the area of a rectangle is necessary.

Example 1: Installation of floor panels.You are planning to renovate a living room with floor dimensions a = 5 m and b = 4 m. You want to find out how many square meters of floor panels you need to purchase.

We use the basic formula: P = a × b.
We substitute the dimensions of the room: P = 5 × 4.
We calculate the result: P = 20 m².
We take into account the allowance for losses (usually about 5-10% for straight laying): 20 m² × 1.05 = 21 m².
Conclusion: You need to purchase 21 square meters of floor panels.

Example 2: Mowing a small field.You have a rectangular green belt with dimensions a = 1500 cm and b = 8 m. What is its surface area expressed in square meters?

First, we unify the units. We convert centimeters to meters: 1500 cm = 15 m.
We use the area formula: P = a × b.
We substitute the standardized data: P = 15 × 8.
We calculate the result: P = 120 m².
Conclusion: The area of the green belt is 120 square meters.

Frequently asked questions (FAQ)

Is a square a rectangle?

Yes, a square is a special case of a rectangle. It has all the features of a rectangle (four 90-degree angles, opposite sides parallel), and its unique feature is that all its sides are equal in length.

What if I have sides in different units?

Before multiplication, it is essential to convert both sides to the same unit of measurement. If, for example, one side is given in cm and the other in meters, it is best to convert centimeters to meters (divide by 100) and only then multiply the sides by each other.

How to calculate the perimeter of a rectangle?

The perimeter of a rectangle is the total length of all four of its sides. Since opposite sides are equal, the formula is: Perimeter = 2 × a + 2 × b or Perimeter = 2(a + b).

How to calculate the area of a rectangle from the diagonal and one side?

The diagonal of the rectangle (d) divides it into two right triangles. Knowing the length of the diagonal and one side (e.g. a), we can determine the length of the other side (b) using the Pythagorean theorem: b = √(d² - a²). After determining the other side, we calculate the area using the formula P = a × b.

How large is the area of 1 are?

1 are (marked as "a") is a unit of measurement of land area equal to exactly 100 square meters (e.g. a square with dimensions of 10 m x 10 m). In turn, 1 hectare (ha) is 10,000 square meters (i.e. 100 ares).