Round tables present special challenges when it comes time to size tablecloths or childsafe edge guards and covers. While owners of square or rectangular tables can simply add up the length of the four sides to find the perimeter, owners of round tables must calculate the circumference to find the distance around the table's perimeter. This process requires only basic math skills and can be accomplished using tools you already have around the house.
Things You'll Need
 Tape measure
 Calculator
 String
 Scissors
 Tape
 Ruler
Method One

Move the chairs out from under the table and set them aside so you can easily access the edge of the table.

Hook the metal lip of a tape measure along one edge of the table, then extend the tape measure across the entire table. Note the measurement across the length of the table at its widest point. This figure represents the diameter of the table.

Multiply the diameter of the table by pi, or 3.14, to find the circumference. A table with a diameter of 8 feet has a circumference of 25.12  8 times 3.14  feet. Note that pi has a constant value and remains the same regardless of table size. It can be used to calculate the circumference of any round table or other circular object.
Method Two

Find a spool of thin string, such as kite string.

Tape the end of the string to the edge of your table.

Unwind the string to wrap it around the outside edge of the table. Use tape as necessary to hold the string in place.

Cut the string from the spool at the point where it wraps completely around the table. Remove any tape to unfasten the length of string from the edge of the table.

Stretch the cut length of string out along the floor and measure its length using a tape measure to find circumference. If you don't have a tape measure, use a ruler and scissors to cut it into 12 inch segments. Add up the length of these segments to find circumference.
Tips & Warnings
 If you need to find the area of your table, multiply pi times the radius of the table squared. Radius equals onehalf of the diameter, or the distance from the center of the table to the edge. You can also find area by multiplying the diameter squared by pi divided by 4, or 0.785.
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