How to measure the circumference of a drawn circle using a thread
Take the thread and place it over the circumference of the circle. And then measure the length of the thread.
The full circle method
Use a sheet of lightweight paper (graph or pattern paper works well) that is at least 1 cm larger all around than the circle you want to draw.
Cut a piece of thread about 4 cm–5 cm longer than your radius.
Tie one end of the thread to a short pencil.
Place the point of the pencil toward the outer edge of the paper with enough room from the edge to make a full sweep.
Measure from where the point of the pencil touches the paper backwards by the length of the radius.
Pin directly through the thread into the paper at that exact point.
Keeping the thread taut, draw a perfect circle using your homemade compass.