Ok, probably too much information just read until you get bored or your head explodes!!
If you want the current fps in the game you are playing bring down the console in the menu screen, ¬ or ~ and type:-
cg_drawfps 1 (enter)
this will display it the top right corner, to get rid of it again change the "1" for "0"
To get a benchmark, you have two standard demos in Q3, firstly bring down the console and type:-
timedemo 1 (enter)
then close the console and choose one of the demos, 001 or 002 and it will play as fast as your system will allow with the current settings. When the demo has finished bring down the console and the last line will give number of frames, time taken & the frames per second. You can change the graphics settings and run it again, but it will default to the standard demo running if you exit the game.
You can also run the demos in a continuous loop to check system stability. There is a batch file for this but I'm not sure where to download it, you can however make a config file yourself.
I'll explain this the best I can but just repost if you are unsure. (copy & paste this into a WordPad doc and print it out if you intend to do this)
go in to C: or Windows explorer and find the Q3 baseq3 folder. (the default path is) C:\Program Files\Quake III Arena.
Open the folder and you'll see the Q3config file. Right click on it and choose copy then right click and choose paste. you will now have a file called copy of Q3config. Left click on this and it will ask you what you want to open it with, scroll down and choose Wordpad.
It should now open with text about the Q3 workings. This file is a copy so you can change it without effecting the program.
from the file edit tab above choose select all (all the text will become highlighted) Hold the mouse pointer over the highlighted text right click, and choose cut.
This should have cleared all the text. Now shut the window down and it will say that the text has been changed, do you want to save the changes? Say yes now right click on your new file called copy of Q3config and click rename. You can call it what you want, something like demoloop, as long as you can remember it.
open your new file and copy / paste the below text that's in bold into it.
set dm1 "demo demo001 ; set nextdemo vstr dm2"
set dm2 "demo demo002 ; set nextdemo vstr dm1"
And save it. This will play demo1 then 2 and loop these until you escape it or it crashes.
Start Quake go into the console and type exec demoloop or exec + whatever name you called your file, press enter.
Demo 001 & 002 are not that taxing on the system though. You can also get some much better benchmarking demo downloads or make you own.
A few other things before benchmarking:-
open the quake 3 config in the baseq3 folder with wordpad and check these (you can find them by using, edit / find / and typing in the name).
r_displayrefresh "xx" where xx is at least 85
you should have Vsync off:-
and set a high fps max:-
if they don't exist you can type them in and save the changes.
It is also probably a good idea to make a copy of the q3 config file to another directory before you mod it so you can get the default settings back again if you need to. Right click on the config file, copy then paste in to another directory, eg:- my documents.
repost if anything is unclear or you need more help, info or demo links as I can't remember where at the moment.
P.s never bothered much with benchmarking UT as it is very poor as a benchmark partly due to the fact it was a glide coded engine to begin with.