Methodology and sources
This project aims to mirror the General Services Administration (GSA) Continental United States (CONUS) per diem structure: a maximum lodging allowance and a meals and incidental expenses (M&IE) component for official travel. CONUS excludes certain non-CONUS locations; Alaska, Hawaii, and U.S. territories are handled under separate rules outside the default CONUS model.
Official sources
- GSA per diem rates (authoritative published rates and bulletins).
- GSA Per Diem API (machine-readable access for building a cached dataset).
- GeoNames postal-code gazetteer (CC BY) for California city names, counties, and sample ZIPs on city pages. Rates still come from GSA ZIP → destination mapping.
What the on-site calculator does
- Resolve the federal fiscal year applicable to each trip date.
- Look up the traveler’s primary destination (locality or ZIP-based mapping where appropriate).
- Apply monthly lodging caps for non-standard areas when GSA publishes seasonal lodging.
- Apply M&IE for the locality and fiscal year, including optional handling for provided meals and first/last day policies, with explicit toggles where agency practice varies.
Mileage is not per diem
Queries like “GSA per diem mileage” mix two reimbursements. Per diem is lodging + M&IE. Privately owned vehicle mileage is a separate FTR rate, usually the IRS standard mileage amount. State employees (for example Washington state mileage reimbursement) may follow a state schedule instead of GSA lodging tables.
What this site is not
- It is not legal, payroll, or financial advice.
- It does not replace your agency’s travel office or internal policy.
- It is not the official GSA website (see sources above).
- It is not a DoD/military JTR per diem calculator (those tables differ from GSA CONUS).
- It may omit edge cases until explicitly modeled and tested.
AI summaries (Google AI Overviews)
This page is intentionally written as plain, citable HTML so automated summaries can extract scope and limitations. Always verify totals against GSA’s published tables for your dates and destination.