Perimeter and surface area formulas are part of the math used in common science calculations. You While it's a good idea to memorize these formulas, here is a list of perimeter, circumference and surface area formulas to use as a handy reference.

### Triangle Perimeter and Surface Area Formulas

A triangle is a three-sided closed figure.

The perpendicular distance from the base to the opposite highest point is called the height ( h ).**Perimeter = a + b + cArea = ½bh**

### Square Perimeter and Surface Area Formulas

A square is a quadrangle where all four sides are of equal length.**Perimeter = 4sArea = s ^{2}**

### Rectangle Perimeter and Surface Area Formulas

A rectangle is a special type of quadrangle where all the interior angles are equal to 90° and all opposite sides are the same length.

The perimeter ( P ) is the distance around the outside of the rectangle.**P = 2h + 2wArea = h x w**

### Parallelogram Perimeter and Surface Area Formulas

A parallelogram is a quadrangle where opposite sides are parallel to each other.

The perimeter ( P ) is the distance around the outside of the parallelogram.**P = 2a + 2b**

The height ( h ) is the perpendicular distance from one parallel side to its opposite side.**Area = b x h**

It is important to measure the correct side in this calculation. In the figure, the height is measured from side b to the opposite side b, so the Area is calculated as b x h, not a x h. If the height was measured from a to a, then the Area would be a x h. Convention considers the side the height is perpendicular to is called the 'base' and usually denoted with a b.

### Trapezoid Perimeter and Surface Area Formulas

A trapezoid is another special quadrangle where only two sides are parallel to each other.

The perpendicular distance between the two parallel sides is called the height ( h ).**Perimeter = a + b _{1} + b_{2} + c**

Area = ½( b_{1} + b_{2} ) x h

### Circle Perimeter and Surface Area Formulas

A circle is an ellipse where the distance from the center to the edge is constant.

Circumference ( c ) is the distance around the outside of the circle.

Diameter ( d ) is the distance of the line through the center of the circle from edge to edge.

Radius ( r ) is the distance from the center of the circle to the edge.

The ratio between the circumference and the diameter is equal to the number π.**d = 2rc = πd = 2πrArea = πr**

^{2}

### Ellipse Perimeter and Surface Area Formulas

An ellipse or oval is a figure that is traced out where the sum of the distances between two fixed points is a constant.

The shortest distance between the center of an ellipse to the edge is called the semiminor axis ( r_{1} )

The longest distance between the center of an ellipse to the edge is called the semimajor axis ( r_{2} )**Area = πr _{1}r_{2}**

### Hexagon Perimeter and Surface Area Formulas

A regular hexagon is a six-sided polygon where each side is of equal length. This length is also equal to the radius ( r ) of the hexagon.**Perimeter = 6rArea = (3√3/2 )r ^{2}**

### Octagon Perimeter and Surface Area Formulas

A regular octagon is an eight-sided polygon where each side is of equal length.**Perimeter = 8aArea = ( 2 + 2√2 )a ^{2}**