this may seem like a dumb question, but are the actual lengths of 2x4x8 studs 8' or are they trimmed from the mill 4.5" to accompany a bottom plate and a double top plate to acheive 8'? is the same true for 9' and 10' studs? thanks for your answers.
Yes there are actual lengths of 8'10'12' and so on studs. You can also order precut lumber. This means that the mill has cut the lumber to your specified length. So if you were building 8'-1" walls, you would get studs that are 92-3/8" long
Your question takes me back to when I was learning framing.
Around here (in the southeast) you can buy 92-5/8" studs to make 8' tall walls or 104-5/8" studs to make 9' walls. No precuts are available for taller walls, but of course you can buy exact 8', 10', 12', etc. and cut as necessary. Note that the 92-5/8" studs, for example, are not trimmed exactly 4.5" from 8' because you want room to insert the ceiling drywall and have a toe jack space at the sole plate so that the lower wall drywall panels can be jacked tight to the upper wall panels.
Carl, once again regionality makes a difference. On the west coast studs for 8' walls are 92 1/4. Studs, in our vernacular, also refers to the pre-cut wall member, so if a carpenter asked for a 9'stud he would expect to get a 104 1/4" inch stick, not something 108". Due to huge demand, finding studs for pre cuts for 8-10' walls is common. When building walls that are multiple heights always take 8'studs and add the wall height to that. Say for instance if a set of plans calls for a 9'6 inch ceiling and a 11' and the rest of them 8' you would make all the stud lengths based on the diff from 8'. So in order to make your 11' ceiling you would add 36 inches to 92 1/4" to get 128 1/4 to build the 11' wall, add 18" to get 110 1/4". What happens is plan designer can either call out a wall as 8' or 8'1". Some may then drop the 1" when detailing taller walls. This can add confusion to some, such as a 9'6 will really be 9'7 but all they really are asking for is a 18" step up. To avoid mix ups or confusion it is therefore always best to add to the stud length rather than build from the full or called out height.
Here in the Pacific Northwest (at least South of Tacoma) we get studs at either 92-5/8 or 88-5/8. If we want "9 foot" walls the studs come at 103-1/2. When you add three plates you end up with exactly 9 foot. Now you can get 54 inch drywall and it would seem logical that two sheets at 54 inches would work out just right but NO!--- now the drywallers have to rip off about an inch to get two sheets to stack and clear the ceiling board. No one has the answer as to why "9 foot" studs don't come at 104-5/8. Go figure!
All the 9ers I've used have been 104 5/8. Some lumberyards custom cut studs. This could expalain some of the variations. All the western Canadian lumbermills cut 92 5/8 and 104 5/8 (that I've seen). However, PT studs always come 93.