Question

formula to calculate area and perimeter for heptagon

Answer 1

AREA =
$\frac{7}{4} \times {x}^{2} \: cot( \frac{180}{ 7} )$
where x is side of heptagon
PERIMETER=
$7 \times x$
where x is the side of heptagon

Answer 2

To calculate the perimeter you just need to add all sides.

Here is the formula for finding its Area: 

$A = \frac{1}{4} \sqrt{5(5+2 \sqrt{5}) a^{2}$ where A = side