I would like to make a perfect circle or donut shape out of wood.?

Um, get a string a pencil and a tack. tie the pencil to one end of the string. Nail the tack, sticking up in the middle of the wood. Tie the string to the tack at a distance that you can trace a circle onto the wood at the diameter of the outside of the donut. Shorten the string so you can trace the circle onto the wood at the diameter of the inside of the donut. There. You have your pattern.

???? You're askign 2 different questions. If you want to make a perfect circle, put a nail in the center of where the center of the circle would be, attached a string to a pencil and attached the other end to teh nail, then go around in a circle. if you don't want to use a nail, then hold the end with your finger. or buy a compass, or ruler that has hole, etc.