This calculator is brand new and may potentially have bugs in it. That said, I have tested it using the DFAS examples here and all the calculations came out correct.
If you find something you think may be wrong with this calculator please let me know via the Contact Me link above.
Official per diem rates: http://www.defensetravel.dod.mil/site/perdiemCalc.cfm
How TLE is calculated: http://www.defensetravel.dod.mil/Docs/perdiem/Computing_TLE.pdf