Methodology and sources

Rate data

• Source: GSA Per Diem API (endpoints rates/conus/lodging/{year} and rates/conus/mie/{year}), fiscal years FY2025, FY2026, FY2027.
• Retrieved: 2026-09-29 (live API call at build time). Each build calls the API again; a dated JSON copy of every response is kept and used if the API is unavailable.
• Check: on September 29, 2026 the FY2027 API data was compared, row by row, with GSA's spreadsheet FY2027_PerDiemRates_Validated090126.xlsx (641 season rows): no difference.
• Coverage: the 48 contiguous states and DC (CONUS). Alaska, Hawaii and territories (Department of Defense) and foreign locations (Department of State) are not included.
• Destinations across years: GSA sometimes renames a destination (for example “Oak Brook Terrace” in FY2026, “Oakbrook Terrace” in FY2027). The site links two years when the name matches, or else when the state and a listed county match. A destination absent from a year's list gets the standard rate for that year.

Rules applied

• Fiscal year: FY N runs from October 1 of N−1 to September 30 of N. Each date uses the rates of its own fiscal year.
• Month: GSA seasonal rates are set by month; each night uses the lodging rate of its calendar month.
• Lodging: actual cost up to the lodging rate (41 CFR §301-11.19). Without a cost entered, the calculator shows the maximum. Taxes are excluded (reimbursed separately in CONUS, §301-11.16).
• M&IE: 75% on the first and last day for trips of 24 hours or more; 75% for a same-day trip of more than 12 hours; nothing for 12 hours or less (§301-11.20). The 75% amount is the one GSA publishes in the M&IE breakdown.
• Meals provided: deducted at the GSA breakdown amount, in full on 75% days, never below the incidental amount (§301-11.21(a)-(b)). Meals from a carrier and complimentary hotel meals are not deducted (§301-11.21(c)).
• Rounding: amounts are computed in cents; no other rounding is applied.

Convention for multi-city trips

The current Federal Travel Regulation says that “generally, the temporary duty (TDY) location determines the per diem reimbursement rate” (§301-11.4) but does not spell out which M&IE rate applies on a day when you move between two TDY locations. The calculator uses one consistent rule: each night's lodging and that day's M&IE use the rate of the place where you lodge that night; the return day uses the rate of your last stop. Your agency or your travel system may apply a different convention: follow it.

GSA also states that reimbursement is based on the location of the work, not of the hotel, unless lodging is not available at the work location. Choose the location of your work.

Not covered

• Reduced per diem prescribed by the agency (§301-11.22), long-term TDY reduced rates, actual-expense authorizations (§301-11.17).
• Joint Travel Regulations (military), IRS high-low substantiation rates for private employers, travel nurse stipends.
• Lodging arrival after midnight: the lodging cost is claimed for the preceding calendar day (§301-11.4). Enter the trip dates accordingly.

City pages

142 destinations have their own page: the 45 largest metro areas with a non-standard rate, and every area whose FY2027 lodging rate varies by at least 30% between its lowest and highest month (where the month of travel matters most). Other areas are in the full table and in the calculator.

Sources

• GSA, Per diem rates and M&IE breakdowns, consulted September 29, 2026.
• GSA, Per diem files (FY2026 and FY2027 rate spreadsheets), consulted September 29, 2026.
• Federal Travel Regulation, 41 CFR part 301-11, eCFR, up to date as of September 25, 2026.
• GSA Per Diem API documentation.

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