TheSnakey wrote:im trying to cut my front door key

why cant someone just give me the cut depths without going threw all this road apples

As MacGyver101 wrote, the root depths in that chart is all you will need.
You have two options.
1. take blank key and your house key and put them in a vise. grab a file and start filing until the keys are identical. Mark your house key with Sharpie before you begin so that you can tell when you are accidentally filing your house key down, which will eventually make that key stop working.
2. grab a blank and mark the centers of each cut based on the shoulder to center of 1st cut distance and then mark the remaining cut centers based on the 1st to nth cut distance. now start filing 1 cut at a time and taking measurements to see when your root depth matches the root depth of your house key. repeat until all cuts are done. even out any peaks and valleys so they aren't too jagged and mis-shapen.
you originally asked about converting to mm.. if you're using a ruler to do this task, then you fail. to do this job with any accuracy, you'll have to do step 1, or if you're really set on making this key from measurements, then you'll need a digital caliper to measure the root depths accurately.

I consider this topic fully explained and the previous posts and charts provided are all you need to do this job. In lieu of your road apples comment, good luck, you will receive no further help from me regarding this topic.
Squelchtone