Can anyone help me to understand toroid geometry?

What is the size and shape (wire is not necessarily round)of the wire. What do you mean by the main radius? You may be able to find the approx. length of wire by doing a scale drawing of the tube and then see how many "wires" you can fit into the cross sectional area. You would then have to find the length of 1 coil (using pi x D) and then multiply this by the number of coils shown on your scale drawing. This method would only give an approx length. Don't forget some coils will be longer than others as you are building up the coil diameter. One question I have is how are you put/wind the wire onto/into the torus?