This question pops up regularly and although the answer is slightly different for every model of car and every tire choice, the formula is really straight forward. So in hopes of teaching you all to fish instead of simply giving you a fish I'd like to explain the process of answering this question for yourself.
First start by going to your favorite search engine (Google, yahoo, duck duck go, etc.) and searching "Ground clearance of (insert your year, make, and model HERE)" We're going to use 2013 Toyota Prius for this example which is 5.3".
Now we're going to take 5.3" and add the lift height, which for our kits is 1.5". 5.3+1.5= 6.8".
Boom! That was easy wasn't it! In less time than it took you to type out "What will my ground clearance be after the lift?" you have your answer!
Now what if we want to add larger tires? Well that gets a little more complicated but still quite simple to find out.
First we need to know what size tires are currently on your vehicle. You can do this by looking at the sidewall of your tire for a string of numbers. Typically something like 195/65R15 or similar. We won't get into what these numbers mean, but they are a breakdown of the width, sidewall height, overall diameter, and rim diameter. Online tools like www.tiresize.com can help guide you through this as well as compare your existing size with your proposed new size. For this specific equation, we need to know the overall diameter, which for this specific tire is 25". Now, say we were looking for a just enough size increase to fill out the wheel well a little more, quiet down the road noise a tad, and give us a touch of additional ground clearance without maxing things out. For this we would want something like a 205/70R15 which has an overall diameter of 26.3". Now here is where it gets a little tricky. Since we're gaining 1.3" of overall diameter but only the bottom half of the tire is below the centerline of the wheel only half of the size increase will contribute to the increase in ground clearance while the other half is helping fill out the gap in the wheel well up top. Now that's what I call team work! ;) So we would divide 1.3" in half and get .65". Then we would take that and add it to our current ground clearance which we found up top to be 6.8". 6.8"+.65"=7.45". TA-DA!
So our new ground clearance with a 1.5" lift and 205/70R15 tires would be 7.45". That's right in the ballpark of Subaru Crosstrek territory! Only without the lack of reliability, poor fuel economy, and less useable cargo space. ;) Nicely done!