In the U.S. Army we run the 2mi and I've been interested in estimating times for this off others, just like how I try to estimate 100m, 200m, and 400m times. It took me a long while to find out the majority of the formulas that the RUN SMART Project uses in its calculator.
They use the original Riegel formula for estimating new times. I expected they might and it was confirmed by receiving a master spreadsheet for their calculator. You can download it here: http://www.electricblues.com/html/runpro.html
Note that the original formula uses a value of 1.06 while a value of 1.15 has been proven to be far more accurate for most people; this is due to the fact that 1.06 has been found to be a "highly optimistic" value to use just as 1.15 has been found to be more realistic. Riegel's formula has its limits like any other formula and thats why alternatives like the Dave Cameron Model exist; it's more useful when concerning ranges of 800m to 10km. I'll be uploading a PDF later of the exact formulas on my site. Look for it right underneath this post referral on my site map. Anyways, here's a calculator I made today to use and offer to you all.