The base of a shape like a polygon is the bottom of the shape. In order to find the area of the base the formula one uses depends on the shape of the object. Here is a list of the most common base area formulas.

### Formulas for finding the Area of Base of Geometric Shapes

Triangle | 1⁄2 b*hb=baseh=height b=base h =height |

Rectangle | length * width |

Trapezoid | 1⁄2 h ( b_1+ b_2 )h = heightb_1=base 1b_2=base 2 |

Square | s^2 s =side |

Parallelogram | base * altitude |

Pentagon | 1⁄2 a*p a = apothemP = perimeter |

Hexagon | 1⁄2 a*p a = apothemP = perimeter |

Heptagon | 1⁄2 a*p a = apothemP = perimeter |

Octagon | 1⁄2 a*p a = apothemP = perimeter |