 Okay, so frequently you'll take a measurement in an experiment but you'll then need to do a calculation using that measurement. For instance, say you measure the mass and the volume of a sample of liquid so that you can calculate its density. You measure the mass on a really accurate balance so you have that value to 5 sig figs, but you measure the volume using a beaker so that measurement is one maybe two sig figs at best. How does that affect the accuracy of your answer? How many sig figs should your answer be? Well, let's say this is your mass and this is your volume and let's put that in the calculator to calculate the density. And the calculator tells us that we have 1.38175 and we're going to put the units in as grams per mill because the units of our mass was grams and the units of our volume was mills and we don't like naked numbers. So the answer that the calculator has given has six significant figures. Now can I really be that accurate in my density value if I only knew the volume to one sig fig? Of course not. The true volume of the sample could be anywhere between 75 and 84 mills and that means that the true value of the density could be anywhere between, you can calculate this for yourself, 1.32 or 1.47. Now if you look at that range it's big enough that we don't know the value of that first decimal place. It could be a three or it could be a four or it could even round up to a five. Hence we're only sure of the first digit of the value of our density, the one. So this leads me to an important point. When you're doing calculations on measurements you're limited by the accuracy of your least accurate measuring device which in this case was the beaker. And a second important point, the calculator is a tool and not a crutch. It will simply do the calculation that you ask it to with no regard to accuracy or sig figs or anything like that. Applying the sig figs correctly is up to you. Don't think that because the calculator gives you something that has 15 decimal places that you should necessarily count all of those decimal places.