What is a Per Diem Calculator?
A per diem ("per day") allowance is a fixed daily amount an employer or organization pays to cover travel expenses such as meals, lodging and incidentals. This calculator adds up the total allowance for a trip by combining full days paid at 100% of the daily rate with travel days (typically the first and last day) paid at a reduced percentage.
How to use it
Enter the daily rate in dollars, the number of full days on the trip, the number of travel days (usually 2 — departure and return), and the travel day rate as a percentage. Many policies — including the U.S. GSA's "first and last day of travel" rule — reimburse travel days at 75%. Adjust the percentage to match your own policy.
The formula explained
The total is calculated as:
$$\text{Total} = (\text{Rate} \times \text{Full Days}) + \left(\text{Rate} \times \frac{\text{Travel \%}}{100} \times \text{Travel Days}\right)$$The first term covers complete days at the full rate, while the second applies the partial-day percentage to the travel days. The two parts are summed for the trip total.
Worked example
Suppose the daily rate is $100, you have 3 full days, 2 travel days, and travel days are reimbursed at 75%. Full days = \(100 \times 3 = \$300\). Travel days = \(100 \times 0.75 \times 2 = \$150\). Total = \(\$300 + \$150 = \$450\) across 5 days.
$$\text{Total} = (100 \times 3) + \left(100 \times \frac{75}{100} \times 2\right) = \$300 + \$150 = \$450$$
FAQ
Why are travel days paid less? On departure and arrival days you are usually traveling for only part of the day, so policies reduce the meals & incidentals portion (commonly to 75%).
Can I set travel days to 0? Yes. If every day is a full day, set travel days to 0 and the total is simply \(\text{rate} \times \text{full days}\).
Is this tied to a specific country? No. The math is universal, though the 75% travel-day default mirrors the U.S. GSA convention. Use whatever percentage your policy specifies.
