Online Calculators: calculate percent error. How to find percent error: To correctly put together the percent error equation, take the difference from accepted value which is also your result minus the accepted value, divide by accepted value and multiply this result by 100.This formula is always expressed as %.xample, total=1,100 and you need to find percent that equals to 100. Using our Percent of Total Calculator answer is 9.09%. GFC and LCM-Math's factor and multiplier. Greatest Common Factor GCF calculator can be used to calculate GFC and Least Common Multiplier LCM calculator to find LCM.