If this is the first time you are calculating perimeter, try a rectangle or a square. These regular shapes will make finding the perimeter easier.
For small shapes you may want to use centimeters or inches, while feet, meters or miles will work better for larger perimeters. Since the opposite sides of rectangles are equal, you will only have to measure one of each set of opposing sides. [5] X Research source
Continuing with the guided example, imagine that in addition to a length of 3 feet, that the width of your rectangle is 5 feet.
So, for the guided example, you would add 3 + 3 + 5 + 5 to get a perimeter of 16 feet (4. 9 m). [8] X Research source You can also use the formula 2(length + width) for rectangles, since the length and width values are doubled. In our example you would multiply 2 by 8 to get 16 feet (4. 9 m).
Square: length of any side x 4 Triangle: side 1 + side 2 + side 3 Irregular polygon: add all sides Circle: 2 x π x radius OR π x diameter. [9] X Research source The π symbol stands for Pi (pronounced like pie). If you have a π key on your calculator, you can use it to be more accurate when using this formula. If not, you can approximate the value of π as 3. 14. [10] X Research source The term “radius” refers to the distance between the center of a circle and its outside boundary (perimeter), while “diameter” refers to the length between any two opposite points on the perimeter of a circle that pass through the circle’s center. [11] X Research source [12] X Research source
The π symbol stands for Pi (pronounced like pie). If you have a π key on your calculator, you can use it to be more accurate when using this formula. If not, you can approximate the value of π as 3. 14. [10] X Research source The term “radius” refers to the distance between the center of a circle and its outside boundary (perimeter), while “diameter” refers to the length between any two opposite points on the perimeter of a circle that pass through the circle’s center. [11] X Research source [12] X Research source
You can use a ruler, measuring tape, or come up with your own example. For the purposes of this guided example, the length and width will be the same as the previous example used to find perimeter: 3 and 5, respectively.
You can divide your diagram into one-unit (feet, cm, miles) segments vertically and horizontally if you want to visualize how the area measurement will look.
You can write the “square units/units squared” notation shorthand as: Feet²/ft² Miles²/mi² Kilometers²/km²
Parallelogram: base x height Square: side 1 x side 2 Triangle: ½ x base x height. Some mathematicians use the notation: A=½bh. Circle: π x radius² The term “radius” refers to the distance between the center of a circle and its outside boundary (perimeter), and the raised two (referred to as the “squared” notation) indicates that the value being squared must be multiplied by itself. [14] X Research source [15] X Research source
