how to calculate square footage of room

Question

Am trying to calculate the square footage of a room in a house to make a bid for painting that room.  Bid will charge by the square foot.  Want to know the formula to do this calculation.

Answer 1

measure the length L and the width W of your room with a measuring tape

let's say L=20ft and W=10 ft

The ares is the product L x W

20 x 10=200 ft^2