 So here are the guidelines for how to apply sig figs to your calculations and before I even start Let me just bring up one more crucial point when you're doing a multi step calculation That is a calculation where you'll get several intermediate answers before you get to your final one Do not round off or apply significant figures until you get to your final answer. This is really important Okay, so here are the rules. When you're multiplying or dividing Look for the number that you've used that has the least number of sig figs You should then round your final answer to that number of sig figs For instance, if we do the calculation 16.35 grams divided by 7.09 mils calculator gives me the answer 2.3060648 etc etc. I'm going to write that down to five or six decimal places I'm going to leave some dots after it to show that it continues on But I know that my final answer can't possibly be that accurate I go back to the values that I used in the calculation 16.35 has four sig figs and 7.09 has three sig figs of those the three sig figs is the lower So that is the number of sig figs that I should express my final answer to So I round that number to 2.31 grams per mil Now when you're adding and subtracting the rule is slightly different rather than looking for the number with the fewer sig figs You're looking for the number with the fewest decimal places for instance, if I add 46.1 meters to 0.901 meters calculator tells me the answer is 47.001 meters But 46.1 has only one decimal place So my final answer must also be rounded to one decimal place So the answer is forty seven point zero meters And let me just remind you again, although I haven't done an example here when you're doing multi-step Calculations wait until you have your absolutely final answer to round off and then go back through all your calculation steps to find the Value that limits your accuracy and then you can round off accordingly