Carpentry and Woodworking - How to estimate ?

I'm going to put new baseboard throughout multiple rooms. Is there a standard rule of thumb for buying the material? Obviously, I need to measure around each room and get a total number of feet. However, I don't want to then try to determine exactly which pieces will be cut from each 12 ft length of trim in order to determine how many pieces to buy. Can I take total length and add a "fudge factor", for instance, 15% in order to get a reasonable approximation?

Sorry if this has been covered before, but when I tried a search on "estimating" I got a database error.

You can do it that way, but a better way would be to do each room separately and then add the total up and include an extra length for fudge. If you have some wall lengths that are, for instance, 10 or 11 feet it would be best to toss the waste, so the fudge factor amount may not be sufficient. Or if you have a long run, say in a hall, of 22 feet again you would have a 2 foot cutoff that would probably not be used.

TG's right, you'll drive yourself crazy trying to get it exact. You will have trim pieces sometimes an inch long, between two adjoining door casings. Measure all the floor space and add in at least 10% or an extra 12' piece.
Not sure what your expertise rating is, but if you are using a pneumatic nailer, work counterclockwise around the room. Don't ask why, it just works better if you are right handed.
Let us know if we can help further.

I make (and save) a cut list for each room, rounding up to the nearest foot for each section. It just takes a couple minutes to do, and saves time & money in the long run.

The cut list will look something like:

NW Bedroom:

14
12
5
7
12

SW Bedroom:

12
10
4
1
10

The benefit of doing that is that you can get the right length of baseboard... and you can optimize it so that you don't have any waste. Nothing worse than getting to the last piece where you need one 12' and have three 4's instead because of poor planning. A cut list helps you avoid that.

In this case, I'd head to the lumber yard looking for 2 @ 14' and 5 @ 12', at a minimum. Many types of base only come in 16' runs, so with a cut list you'd just pair up the cuts to figure out how many 16's you'd need. You rarely will put a splice on a wall if it doesn't need one. Using full pieces on each wall is best.

I don't like waste, don't like leftover trim, don't like extra trips to the lumberyard to either get more or return extra.

I have to agree with xsleeper. This stuff is not cheap usually over a buck a foot, so if you end up with a lot of 8" pieces you're wasting a lot of money. Take the time to measure out each room and then do a cutting plan. Depending on where you shop you might have to buy the molding in 8 foot or longer lengths (Home Depot lets you cut what ever length you want). If you were building a cabinet you wouldn't just start cutting into a piece of 3/4" walnut plywood without determining the most efficient use would you? Same thing here unless of course money is not an object in which case you could have some do it. I'm so cheap I make my own molding:wall: but then again I can match the existing wide moldings in the house and only pay a fraction of what custom work would cost.