Please be aware that this calculator assumes maximum shrinkage rates for PMC and Art Clay as specified by each manufacturer for their products. We do not guarantee any accurate results in shrinkage. Many conditions can affect actual shrinkage rates of metal clay. These factors can be and are not limited to thickness,size,firing temperature and clay condition.We would suggest checking the accuracy of the ruler the first time you print one against an actual ruler. It should be considerably accurate across the table but minute differences between different printers may occur. This calculator is not currently suggested for ring shrinkage calculations. There are different considerations with rings that will be addressed with future release's of this calculator.