# Area

## Area

Measure of a two-dimensional closed surface.

• Synonym for surface area.
• The term surface area is generally used in the case of large surfaces.
• Area is a quantity that is almost always expressed using denominate numbers.

### Examples

• The side c of a square measures 10 cm.
The area A of this square is 100 cm², because: A = c × c = 10 × 10 = 100.
• A rectangle measures 8 cm long (a) and 6 cm wide (b).
The area A of this rectangle is 48 cm², because: A = a × b = 8 × 6 = 48.
• The radius r of a circle measures 10 cm.
The area A of this circle is 100π cm², because: A = πr² = π × 10² = 100π.

### Notation

The basic unit of area in the International System of Units (SI) is the square metre, noted as .

The relationship among the different units of area are:

 km² hm² dam² m² dm² cm² mm² 0.000 001 0.0001 0.01 1 100 10 000 1 000 000

### Educational Note

The area of a figure is a measurement, so we should say the area of a square or the area of the surface of a square.