The perimeter is defined as the distance around an object. For example, if measuring the perimeter of a football field, you would measure the entire edge of the field. If measuring a more unusually shaped object, you would need to be careful to measure and add together the length of each individual side to ensure you have the length of the entire distance around the shape.
Add together the lengths of each side of a shape to find its perimeter.
Multiply the diameter of a circle by pi (3.14) to find the circumference or perimeter of a circle. The diameter is the distance across the circle. Alternately, you can multiply 2 times the radius times pi. The radius is the distance from the middle of the circle to the edge.
Use a unit of measurement to find the perimeter of an object with sides of unknown length. Smaller objects can be measured with a ruler, while larger objects may require the use of a yard stick or tape measure.