I never heard of a conversion chart before. I bought the Mettler silk wrapped thread sample chart because that is the thread I use. Not sure how accurate these comparisons are. I do most of my shopping online and you can't trust the color you see on your monitor. If you are using Aurifil thread now, I would just go and purchase their thread sample chart. I just bought one for Superior Nature Colors for only $3.00 from Superior threads.