i've got a 1" threaded stem.
is there a standard handlebar width that fits said stem or a way to tell what size to get?
or should i just take it to LBS to get it measured?
p.s. i'm looking at drop bars.

I'm assuming you mean bar clamp diameter rather than width of bars . If so,there is no standard for 1" threaded. I've seen everything from 25mm to 26.4. But if it's relatively new, chances are it's likely 25.8/26.0. But you don't waste money by measuring and knowing for sure.

Drop bars fitting your stem should come in various sizes. Choosing the right one is not straightforward (if you don't currently own a bar that suits you and might be 'replicated'). It's often said that handlebar width (usually measured in cm's) should correspond with the width of your shoulders. Many riders prefer a slightly wider bar; some pick a slightly smaller one.

Sorry, craiginho. Upon closer reading, Sydney's assumption seems correct. Please ignore my post re: handlebar width.

A good manufacturer of bars, such as 3TTT(.com) produce them in a variety of widths, drop radii and curve styles. The clamp diameter is also given in their geometry charts, and they make stems to match, in a variety of length.
The usual range of bar width is from 36 to 48cm, with the "std" being 42cm. There is no "correct" way to size a bar, but many people match them to the width of their shoulders, measured at the center of socket joint.

sorry for confusion, you're correct.
had it measured and the wrench says it's 25.4mm.
in looking at handlebars on performance there are no options when it comes to clamp diameter.
what gives?

25.4 is the standard for mountain bikes which typically use flat and riser type bars. 25.4 use to be a fairly common oriental size for drop bars,but that standard is pretty much out of print now. Nitto still makes a 25.4 drop bar.Alot of folks force a 26.0 bar into a 25.4 clamp and get away with it,but it isn't recommended practice.