Rectangle area calculator

Find rectangle area by multiplying length and width. Enter both measurements in the same unit, see the result and check the formula and example.

What do you want to find?

Base cm

Height cm

Units and conversions

Input unit

Results in

Results update as you type.

Result

Why this result?

Area measures the space inside. A square with sides of 1 cm covers 1 cm²; perimeter measures the boundary.

How do you calculate the area of a rectangle?

Area is the surface enclosed by the four sides. Multiply the base by the height: picture a grid of columns and rows of unit squares.

A = b \times h

A is the area, b the base and h the height. Both sides must use the same unit; the result uses that unit squared.

Example: the floor area of a room

A room measures 420 cm by 350 cm. To find its area in square metres, first convert both sides to metres.

From dimensions to floor area

Dimensions: $420 cm \times 350 cm$
Surface area: $14.7 m^{2}$

Steps

Divide each length in centimetres by 100.
$420 \div 100 = 4.2 m$
Convert the height to metres as well, dividing by 100.
$350 \div 100 = 3.5 m$
Multiply the lengths in metres: metres times metres gives square metres.
$A = 4.2 \times 3.5 = 14.7 m^{2}$

The floor covers 14.7 m². This is the geometric area; allow separately for cuts and waste when buying flooring.

Area and perimeter: what is the difference?

Use area to cover the floor. Use perimeter to measure the boundary of the room: twice the sum of the base and height.

P = 2 \times (4.2 + 3.5) = 15.4 m

One room, two measurements

Area
14.7 m²: the floor surface to cover.
Perimeter
15.4 m: the total length of all four sides.

How to get the area in square metres

Convert the sides to metres before multiplying, or convert the area afterwards. Since 1 m equals 100 cm, a square with 1 m sides contains 100 × 100 squares of 1 cm².

To convert cm² to m², divide by 10 000, not 100. In the calculator, “Results in m” gives the area in m² and the perimeter in m.

Already know the area? Divide it by the height to find the base, or by the base to find the height. The side used as the divisor must be greater than zero.

1 m^{2} = 10000 {cm}^{2}

Precision and special cases

Sides from 0 to 10¹²; input area up to 10²⁴, in the selected units. Results rounded to 12 significant digits.

If a change of mode or input unit exceeds numerical limits, it is rejected and the previous measurements are kept. Positive values too small to represent are not treated as zero. Edit a measurement or choose another option to resume calculation.

For inverse calculations, area uses the square of the input unit. A known side of zero cannot determine the other side.

The grid uses the input unit and appears up to 20 units per side.

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Rectangle area calculator

Result

Why this result?

How do you calculate the area of a rectangle?

Example: the floor area of a room

From dimensions to floor area

Steps

Area and perimeter: what is the difference?

How to get the area in square metres

You might also need

Circle area

Circle circumference

Triangle area