To estimate TDY per diem, find the official rate for your duty location and travel dates, separate lodging from meals and incidental expenses (M&IE), then apply your trip's lodging requirements, meal status and travel-day rules. Multiplying the maximum daily rate by the number of days usually misses important details. JTR 020301–020309
The worksheet below is a planning aid, not an official TDY per diem calculator or reimbursement approval. It covers a routine multiday trip under the standard lodging-plus method. Special duty, leave, actual expense allowances and other exceptions require additional treatment.
Start with the correct official lookup
| Duty location | Rate source |
|---|---|
| Contiguous United States and Washington, D.C. | GSA domestic per diem lookup |
| Alaska, Hawaii and U.S. territories or possessions | Defense Department nonforeign OCONUS rates |
| Foreign location | State Department foreign per diem rates |
Use the DTMO per diem page to reach the relevant rate resources. The GSA trip-planning lookup accepts location and dates and explains the domestic locality boundaries.
Choose the actual duty location, not a more expensive nearby city or simply the hotel's address. GSA bases the rate on the work location, with an agency-authorized exception when lodging is unavailable there. A base spanning multiple localities can also require checking the boundary rule. Record the location selected and the dates used rather than saving only a dollar amount.
Check the dates, not just the city
Look up each portion of the stay if rates change during the trip. A seasonal lodging rate or fiscal-year boundary can make a single nightly figure inaccurate. The federal fiscal year begins October 1, so a trip in October belongs to the following numbered fiscal year. GSA's lookup allows date-based searches, which avoids selecting the wrong fiscal-year table. GSA per diem lookup and files
Save the source and effective dates with your estimate. Recheck before finalizing the authorization if the trip changes.
Work out lodging one night at a time
Under the standard method, estimate eligible actual lodging costs up to your applicable ceiling. Required government lodging or ILP rates can make that ceiling different from the locality maximum. An unused part of the lodging allowance is not extra cash paid to you. JTR 020301 and 020303
List each night, quoted room charge and applicable limit. Handle taxes separately for CONUS and nonforeign OCONUS; include lodging taxes within the lodging calculation for foreign locations. Keep other fees identifiable for their own eligibility review. JTR Table 2-15, rules 12–13
Apply the correct M&IE treatment
For ordinary travel of more than 24 hours, first and last travel days generally use 75% of the applicable locality M&IE rate. This is not 75% of the hotel allowance. Full TDY days can involve locality M&IE, government meals, a proportional meal rate or other applicable adjustments. JTR 020304 and 020309, Table 2-20
Before estimating full-day meals, check the authorization and reporting instructions. A rate website cannot determine which government meals are available or directed for your assignment. If the meal status is unclear, keep it marked “to confirm” instead of presenting the estimate as final.
A simple five-day estimate
Assume a Monday departure, Friday return, four lodging nights at $100, an applicable $120 lodging ceiling and $80 locality M&IE. Assume all three full TDY days qualify for full locality M&IE, with no leave, furnished-meal adjustment or special allowance. These amounts are invented, not current rates for any destination.
| Component | Calculation | Estimate |
|---|---|---|
| Lodging | 4 nights × $100 | $400 |
| First and last travel-day M&IE | 2 × ($80 × 75%) | $120 |
| Full TDY-day M&IE | 3 × $80 | $240 |
| Subtotal | $400 + $120 + $240 | $760 |
Taxes, other reimbursable expenses, airfare and rental cars are excluded. Using the $120 room ceiling instead of the $100 actual charge would overstate this example by $80. Counting five hotel nights would also be wrong: travel days and lodging nights are different inputs.
Why DTS may show less than your estimate
Compare inputs before assuming DTS is wrong. Check the duty locality, dates, actual room amount, required-lodging limit, travel-day percentages, meal availability and any leave days. Then ask your travel office about the specific line that differs. The JTR governs the entitlement; the public rate lookup supplies only part of the calculation.
For a school TDY, classmates may help you identify practical questions about dining access and arrival arrangements. TDY Spy is being built for those class connections. Use official guidance to settle your rate and authorization, and keep financial records in the official travel process.