To determine how many grams are in a mole, you must first convert the grams to moles. The formula is: Number of moles=(no. of grams) / (molar mass), then the Number of grams= (No. of moles) times (molar mass). In order to determine the number of grams, the type of element would be needed. Using carbon as an element, then one mole is equivalent to 12.01 grams.