Per Diem Calculator
Trip total for lodging and meals using daily per diem rates, including the 75% first and last day meal rule.
What it does
A per diem is a fixed daily allowance for travel costs, used by federal agencies and many companies that follow the same structure. It has two parts: lodging, which is paid for each night, and meals and incidental expenses, usually shortened to M&IE, which is paid for each travel day. The rates come from tables that change by location and season.
The day count and the night count are not the same. A five day trip that leaves Monday and returns Friday has four nights. Lodging is owed for the four nights, while meals are owed for all five days. Mixing those two numbers is the most common reason a per diem estimate comes out wrong.
Travel days get a partial meal rate. The first and last days of a trip pay 75% of the M&IE rate because the traveler is usually in transit for part of the day. Full days in between pay 100%. For a five day trip, that works out to three full days plus two 75% days, or 4.5 full M&IE days in total.
The default example uses a $110 lodging rate and a $68 M&IE rate. Four nights of lodging cost $440.00, and 4.5 meal days cost $306.00. The trip total is $746.00, which averages $149.20 for each of the five days. A single day trip with no overnight pays only 75% of M&IE.
These figures are allowances, not a promise of profit. If the hotel costs more than the lodging rate, the traveler covers the difference unless the agency approves an actual expense. If meals are provided at a conference, the M&IE amount is usually reduced for those meals. The calculator shows the standard allowance before those adjustments.
How to use
- Count the travel days from departure to return, including both travel days.
- Count the nights you will actually pay for a hotel.
- Look up the lodging rate for the duty location and travel month.
- Look up the M&IE rate for the same location.
- Enter all four values and read the trip total.
- Check the meals total against any provided meals that should be deducted.
Formula
- lodging
- Nightly lodging allowance for the duty location, in dollars.
- nights
- Number of nights with a lodging cost.
- M&IE
- Daily meals and incidental expenses rate, in dollars.
- days
- Number of travel days, including the first and last day.
- M&IE days
- Full rate equivalents after the 75% first and last day rule.
The 75% rule applies only to M&IE, never to lodging. A one day trip with no overnight stay pays 0.75 of the M&IE rate and no lodging. The standard GSA M&IE rate also includes a separate incidental portion, which is not broken out here because the total is what gets reimbursed.
Worked example
Example: 5 days and 4 nights at $110 lodging and $68 M&IE
Defaults: 5 days, 4 nights, $110 per night lodging, $68 per day M&IE.
- Lodging: 4 nights x $110 = $440.00.
- M&IE days: 5 - 2 full days + 1.5 partial days = 4.5.
- Meals: 4.5 x $68 = $306.00.
- Trip total: $440.00 + $306.00 = $746.00.
- Average per day: $746.00 / 5 = $149.20.
- First day pays $51.00 of M&IE, the last day pays $51.00, and the three middle days pay $68.00 each.
Reference table
| Days | Nights | Lodging | Meals | Total |
|---|---|---|---|---|
| 1 | 0 | $0.00 | $51.00 | $51.00 |
| 3 | 2 | $220.00 | $170.00 | $390.00 |
| 5 | 4 | $440.00 | $306.00 | $746.00 |
| 7 | 6 | $660.00 | $442.00 | $1,102.00 |
Limits
- Uses the rates you enter; it does not look up current GSA rates by city or month.
- Assumes one location for the whole trip, while real trips can span several rate areas.
- Does not deduct meals that were provided at a conference or included in a registration fee.
- Does not cover actual expense approvals, transportation, or incidental costs outside the M&IE rate.
Common mistakes
- Paying lodging for the last day, when the trip ends that morning.
- Paying full M&IE for the first and last travel days.
- Using the home city rate instead of the duty location rate.
- Counting a partial travel day as a full day in both directions.
- Forgetting to reduce M&IE when a conference provides lunch or dinner.
Try it yourself
Quick checks. Answers sit tucked under each question.
3 days, 2 nights, $150 lodging, $80 M&IE?
Lodging $300.00, meals $200.00, total $500.00, average $166.67 per day.
1 day with no overnight, $200 lodging, $70 M&IE?
Lodging $0.00, meals $52.50, total $52.50, average $52.50 for the day.
7 days, 6 nights, $95 lodging, $60 M&IE?
Lodging $570.00, meals $390.00, total $960.00, average $137.14 per day.
Questions
What is a per diem?
A fixed daily allowance for lodging and meals while traveling on official business. Agencies set the rates by location and time of year.
Why are the first and last days paid at 75%?
Those days usually include travel, so the traveler is not eating all meals at the destination. The reduced rate reflects the partial day.
Does the 75% rule apply to lodging?
No. It applies only to the M&IE portion. Lodging is paid for each night at the full location rate.
How many nights should I claim?
Count only the nights you pay for a hotel. A Monday to Friday trip normally has four nights.
Are per diem rates the same everywhere?
No. Rates vary by city and county and sometimes by month, especially in seasonal destinations. Standard rates apply where no special rate is listed.
Do I need receipts?
For the standard per diem, no receipts are needed for meals. Lodging usually requires a receipt, and actual expense claims always do.
Sources
- GSA: Per diem rates frequently asked questions
- GSA: M&IE breakdowns
- IRS Publication 463: Travel, gift, and car expenses