🧳 Per Diem Calculator

Base formula (75% option off, or a single-day trip): Total = (lodging rate + meal rate) × number of days. For example, a $70 lodging rate + $30 meal rate ($100/day combined) over a 3-day trip totals $300.

With the 75% option on and a trip of 2 or more days (referencing the U.S. GSA "First and Last Day of Travel" rule): Total = lodging × days + meals × (days − 2) + meals × 0.75 × 2. Lodging is always paid at 100%, even on travel days — only the meal rate drops to 75% on the first and last day. For example, with a $70 lodging rate, $30 meal rate, and a 3-day trip: lodging total = $70 × 3 = $210; meal total = $30 × 1 (the one full-rate middle day) + $30 × 0.75 × 2 (first and last day) = $30 + $45 = $75; grand total = $210 + $75 = $285.

If you don't need a separate lodging line, leave the lodging rate at 0 and put your entire daily rate in the meal field — the 75% option then applies to that whole combined rate.

The U.S. General Services Administration (GSA) sets federal per diem rates and applies a "First and Last Day of Travel" rule under which only the M&IE (Meals & Incidental Expenses) portion is paid at 75% on travel days, while the lodging rate is unaffected by this rule and is reimbursed at its normal rate. The logic is that travelers have fewer meal opportunities at the destination on days spent partly in transit. This calculator does not replicate GSA's official location-specific rate tables — it simply offers the same mechanic (75% applied to meals only) as a reference model that any organization can use with its own configured lodging and meal rates, not just U.S. government trips. Always check your organization's current official travel policy before relying on this general-purpose tool for actual reimbursement.