See exactly how MyPerDiem calculates.

CONUS data path

A validated location, fiscal year, and month are sent to this server. The server requests GSA’s public Per Diem API, normalizes the returned lodging and M&IE values, and supplies the applicable meal breakdown. Successful responses are cached temporarily to reduce upstream load. If GSA is unavailable, the calculator asks for manual entry rather than fabricating a current locality rate.

Trip arithmetic

1. Days and nights: inclusive calendar days from departure through return; nights equal days minus one.
2. Lodging: nights multiplied by the lower of actual nightly cost or the entered authorized ceiling.
3. Travel-day M&IE: one day for a same-day estimate or two days for a longer trip, multiplied by the entered travel-day percentage.
4. Full-day M&IE: full days multiplied by the daily rate, less selected furnished-meal deductions, with the entered incidental amount preserved as the floor.
5. Total: allowed lodging, entered lodging taxes or fees, M&IE, and entered other expenses. The advance figure is a user-selected planning percentage, not an authorization.

Important model boundaries

The model assumes one primary locality and one nightly lodging amount. It does not model itinerary changes, leave, personal deviations, partial days by hour, dual lodging, proportional tax limits, actual-expense authority, constructed travel, government-quarters rules, exchange-rate settlement, dependent categories, or agency-specific business rules. Those cases need separate calculation or official system review.

Editorial and source policy

Numerical claims are checked against primary government sources whenever available. Pages identify the source family and review date. We do not copy official guidance as a substitute for explanation; the site adds a transparent calculation, decision checks, and warnings about where the model stops. A source conflict is resolved in favor of the current official source.

MyPerDiem does not use a hidden “AI entitlement decision.” The formulas are deterministic browser code. Software and editorial drafting may use automated tools, but Moulton Holdings LLC reviews source links, formulas, and deployment tests before publication. No entered itinerary is uploaded except the limited location and period fields required for a requested GSA lookup.

Release validation

Before deployment, the project smoke test checks route-specific server-rendered content, canonical URLs, structured data, versioned assets, security headers, robots.txt, the sitemap, ads.txt, unknown-route handling, redirects, and representative GSA lookups. Calculator rate constants and worked arithmetic are compared with the linked effective-date tables. A passing test proves the implementation behaved as designed; it does not replace the traveler-specific official review.