I am replacing a few interior doors and I need to know if the existing door is Right Handed or Left Handed so I have them drilled correctly. Sounds like the acronyms for this are RH and LH. This also would apply for new pre-hung doors as well I assume as they are all marked that way at the mega home improvement stores.
Not only besides RH or LH, you need to determine swing direction. Trust me, this needs to be agreed upon. When I built the additional room onto my house, I thought 84 Lumber understood the direction of door swing and they didn't. There is left inswing, right inswing, left outswing, and right outswing.
The door handle on my exterior door is on the right-hand side, but it is considered a left-hand outswing. Whereas my front door swings in, and the handle is on the right hand side so it is considered a right-hand inswing. Make sure you know what you are buying before you spend the money!
As a homeowner, I have installed many doors, and every time I do I have to re-learn how to "determine door swing". Just make sure you write it down before you order the door, it is easy to get confused again when you go to your local home improvement store. This website should help:
First, the SIMPLE WAY to determine door handing...
IF YOU ARE REPLACING AN EXISTING DOOR: With the door open, stand with your back against the hinge jamb. If your left hand is nearer the doorknob, then the door is LEFT-HANDED. If your right hand is nearer the doorknob, then the door is RIGHT-HANDED.
IF YOU ARE INSTALLING A NEW DOOR AND JAMB IN A ROUGH OPENING: Decide which side of the frame will have the door hinges. Stand with your back against the hinge-side of the frame and extend an arm in the direction you wish the door to open. If you extended the left arm, then you need to order a LEFT-HANDED door set. If you extended the right arm, then you need to order a RIGHT-HANDED door set.
IF THE DOOR IS GOING TO BE AN EXTERIOR DOOR... Though exterior doors typically swing inward, outswinging exterior doors are available. So be sure to add "inswinging" or "outswinging" to your notes before ordering!
..if you are still confused, just Google: "determine door swing".
With the door closed, stand on the hinged side of the door. If you can see the hinges with the door closed you are on the hinged side of the door. If your left hand is closest to the door knob it is a left hand door. If your right hand is closest to the door knob it is a right hand door. This method works in the store where the doors are strapped shut. On exterior doors make sure some one didn't set the door down upside down; this will change things a bit.
whether a door is an exterior or iinterior door the designation is the same. Think of RH as right hinge. if the door is swinging away from you the hinge is on the right side. for a left hinge door, if the door is swinging away from you the hinges are on the left side. Inswing or outswing only matters with exterior doors where they have a sill. The handing or hinging is still determined the same way.
It's best explained on this page: http://www.specialtydoorhardware.com/door-handedness/
Left Hand – Hinges on the left, opens inward.
Left Hand Reverse – Hinges on the left, opens outward.
Right Hand – Hinges on the right, opens inward.
Right Hand Reverse – Hinges on the right, opens outward.
Aside from the accepted answer regarding exterior doors, there appear to be a lot of convoluted answers regarding interior doors and their 'handedness.'
Stand (or imagine you're standing) facing the closed door, on the side (front/back) of the door where you can see the hinges (i.e. the door would open toward you.)
From this position, the side (left/right) of the door with the handle/knob (opposite the hinges,) is the same as the 'handedness' of the door.
Stand in such a way that the door will swing open towards you.
The handedness of the door is the hand that one would naturally use to grab the doorknob to pull the door open.
Inswing and outswing have to do with the way the jamb is constructed and the orientation of the lock bolt. If you're installing interior doors in an existing frame, and doing the lockset yourself, then there's no need to worry about in and out swings. If you're ordering pre-hung interior doors, again it doesn't matter, but make sure you're standing on the right side of the opening when you make your decision.
I modified 0A0D's image with some "L --- ^ --- R" labels . The V or ^ indicates which way you are facing.