I make this guarantee - ALL of my calculations are 100% correct. The reason I know this is that whenever I make a change to any formula, I test my results against two other segment calculators just to make sure that I haven’t made an error.
One common mistake new users make regards the board length. It is logical to think that if the SEL is 1”, for example, and you need 12 segments, you have to have a board that is 12” plus saw kerfs but that is not correct. If you are using a wedgie sled with two fences or a single-fence sled, be aware that you are cutting a segment that is a trapezoid that has two Segment Edge Lengths - a long one that forms the outside diameter and the short SEL that makes the inside diameter. When you cut a board into segments, the first one you cut will have one long SEL cut from one side of the board and it is followed by one with the short SEL cut from the same side of the board. So if you cut a board into 12 segments, the formula for the board length is 6 times the long SEL plus 6 times the short SEL plus 11 saw kerfs cut at 15 degrees.
I don’t add anything to the board length for clamping and safety. I simply show you the absolute minimum length a board must be to yield the number of segments you have specified. It is up to you to know how much wood you want to add for clamping and safety.
The good thing to know about this is that if the software says that your outside diameter is calculated to be 9.5”, for example - if yours isn’t 9.5” it means that one or more of your segments did not get cut at the correct SEL. The formula for calculating SEL is simple and is widely known.
I am more than glad to use zoom video to share your screen. If you would like to do so, please install zoom and then call me at the phone number listed at the bottom of every page of the main website.