Methodology & data sources

Perdiemify is a free per diem calculator for federal, TDY, and corporate travelers. Here is exactly where our numbers come from and what they mean.

Where the rates come from

Continental U.S. (CONUS) lodging caps and M&IE rates come directly from the U.S. General Services Administration (GSA) per diem API for fiscal year 2026 (effective October 1, 2025 through September 30, 2026). Hawaii and Alaska are non-foreign OCONUS areas set by the Department of Defense, not the GSA — those rates come from the DoD / Defense Travel Management Office (DTMO) non-foreign per diem bulletin, and Alaska's caps vary by season. Together we cover 416 cities and areas across all 50 states and the District of Columbia. CONUS areas without a specific rate fall under the GSA standard CONUS rate.

Lodging vs. M&IE — what you keep

These two parts of per diem work differently, and the distinction matters:

• Lodging is reimbursed at your actual cost, up to the nightly cap. You submit receipts, and there is no upside to spending less — you are simply reimbursed what you paid.
• M&IE (meals & incidental expenses) is a flat daily allowance. For most travelers it is paid regardless of what you actually spend, so the amount you do not spend is yours to keep.

That is the “keep the difference” idea — it lives in M&IE, not lodging.

The 75% first/last-day rule

On the first and last calendar day of travel, M&IE is paid at 75% of the daily rate. When a meal is provided (for example, a conference-furnished lunch), that meal's portion is deducted from the day's M&IE.

Rate source for military travelers

For CONUS, Perdiemify uses GSA standard federal rates. For Hawaii and Alaska we use the DoD non-foreign OCONUS per diem (DTMO). We do not compute Joint Travel Regulations (JTR) specifics, foreign-country OCONUS rates, or DTS allowances, so military users should treat our figures as the published GSA/DoD locality rates and confirm specifics in DTS or with their travel office.

Independence & disclaimer

Perdiemify is an independent tool. It is not affiliated with, endorsed by, or sponsored by the GSA, the U.S. Department of Defense, or any government agency. Rates are provided for planning purposes and are not official travel guidance. Always confirm against your agency's travel system before filing.