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 **m²**.

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**.