I have read contradictory explanations on determining door handedness so need a little help. If with the exterior door open I stand with my back against the hinges and the door knob is closest to my left hand, then is the door left handed and in-swing? If not, then what is it?
Door handing descriptions vary, so my best advice is to draw a picture for your door supplier and let them decide what they call it.
From Schlage.com (https://www.schlage.com/blog/categories/2017/01/understanding-lever-door-handing.html): you'll need to stand on the outside of your door. Notice where the hinges are.
If the hinges are on the left, you have a left handed door. You will need a left handed (LH) lock.
If the hinges are on the right, you have a right handed door. You will need a right handed (RH) lock.
(follow the link for useful pictures)
So, assuming that your exterior door swings into the house (which is a pretty safe bet, I'd say), when you stand outside, if the hinges are on the left, it's a LH door; if the hinges are on the right, it's a RH door.