General Services Association (GSA) manages US Federal travel. In order to comply with the e-gov initiative, in 2000 through 2004 I worked with GSA to provide hotel information to all government travelers from GSA's website by designing advertising-funded website with no cost to tax-payers. (Pin links to current GSA travel site)
Do you need a free per diem calculator? My best friend explained me this product is generally used for taxpayers in the aviation or airline industry, and all travelers might find it beneficial. If you need per diem rates including lodging, we suggest reviewing Per Diem Methods and Rates page.
Per diem rates are broken down into three parts- CONUS (domestic), OCONUS (Hawaii, US territories, etc.) and International. Several per diem allowance rates exist, and it is important to choose the correct one.