Here you go: 2.613.
                                                    Constants and Formulas for Calculating Common Offsets

                                                                       ELBOW FITTING ANGLES

                            72 degree     60 degree     45 degree     30 degree     22.5 degree     11.25 degree     5.625 degree     
                            Elbow          Elbow           Elbow           Elbow          Elbow              Elbow               Elbow

Travel = Offset X      1.052          1.155           1.414           2.000          2.613              5.126               10.187

T = Run or Rise X      3.236          2.000           1.414           1.155          1.082              1.019               1.004

R or R = Offset X      0.325          0.577           1.000           1.732          2.414              5.027               10.158

R or R = Travel X      0.309          0.500           0.707           0.866          0.924              0.980                0.995

Offset = Travel X      0.951          0.866           0.707           0.500          0.383              0.195                0.098

Offset = R or R X      3.078          1.732           1.000           0.577          0.414              0.198                0.098

Note:   R or R: Run or Rise   T: Travel

Hope this helps...  Reference: IPT's Pipe Trades Training Manual By Robert A. Lee One of my favorites for pipe fitting!!! :) :) :)

http://www.pipefitter.com/existing_php/IPT.php

Here's software you can upload to your PDA like palm or similar... This software enables you to do all types of pipe fitting calculations anywhere!!!

http://www.americanpipefitter.com/

Take a look at some of the sample calculations this software can do on your PDA:

http://www.americanpipefitter.com/Calculations.html

If you do a lot of pipe fitting but are not that good in math, and need the answers to the "calc's" right away then this software is for you!!!

Here's the US Army's plumbing & pipe fitting manual... Scroll down to page 6-5 to 6-7 and you shall find basically the same infor as above and more:

http://www.scribd.com/doc/2513896/Army-fm3-34x471-Plumbing-PipeFitting-and-Sewerage

Here's the link to the actual .pdf file:

http://www.mydiscounttools.com/estore/articles/plumbing/fm3-34.471.pdf

Respectfully,
Henry

Hey Longarc-
If you are looking to improve your understanding of pipe fabrication there is book you need to get.  It's called Pipefitters Math Guide, by Johnny Hamilton.  It is, IMO, the most understandable, best written, most clearly explained text on the subject.  Every job I've done in the last 15 years I have at some point, when trying to explain how the dimensions for an offset were determined, to a helper looking to learn or a welder that was wanting to improve his fitting skills, I have broken out this book and showed it to them and pointed out the section where the information and applicable math was theirs for the asking.  I always keep a copy in my truck, both as an excellent reference and to encourage younger hands to take the time and learn the essential understanding of applied math as it relates to our trade.  Here's the beauty of it- it was written by a for real pipefitter, it starts with the very basics and the premise that the reader either never learned or has forgotten the bascis, ie. adding/subtracting/converting fractions, whole numbers and fraction, decimals, converting decimals to fractions and back and goes on from there.  Every subject is broken down into small 3-4 page chapters in completely understandable text and there is a short quiz at the end of the chapter to test yourself with the answers in the back of the book.  After the basics it moves on to the application for pipe fabrication- the right triangle [the basic geometry all calculations are determined by], it explains how and why we use it, it's elements and how to derive them, how to determine any side of the triangle or any angle- this is the set, run, travel you were asking- and most importantly how you can calculate those parts from what you know instead of looking it up on a chart, which is important because 1] sometimes the charts are wrong, 2] knowing how to find those dimensions will make the big picture clear to you, improve your overall understanding of fabrication and give you a well founded, rock solid confidence of your abilities as a fitter- worth the price of the book itself. It goes through the circle, how that is used in our trade, through rolling offsets and how to solve them and you can do it as home study.  By the time you finish with it you could pass the NCCER test with confidence or ny jobsite exam they are giving fitters- KA-CHING.  From your post it sounds like you have some of the basics down at the very least and are competently getting along.  If you are really interested in taking your trade to the next level you will do yourself a life long favor by getting this book.  The writer understands that a lot of us in this trade were not stellar students and he is able to explain the concepts so clearly and the book is so well organized I can assure, whatever few last gaps there may be in your pipe fabrication knowlege will be filled in and anwered to a journeymans level of understanding.  It can be ordered through Barnes and Noble or Borders if not in stock and believe me brother, for $25 it will be the best tool you ever put in your gangbox- the foreman will be coming to you for answers on how to lay out that 37 1/2 degree fitting from a 45- and you'll know how. This book honed the final edge on my fitting knowlege and I can't reccomend it enough.  Best of luck.