Per Diem Calculator

Overview

How to use this calculator

1. Enter the full‑day per diem rate allowed by your employer or by the GSA/IRS or other official guidelines for your destination.
2. Enter how many full days you’ll be away—days where you are entitled to 100% of the per diem under your policy.
3. Enter how many travel days you have (typically departure and return days where a reduced per diem applies).
4. Adjust the travel‑day percentage if your policy differs from the default 75% (for example, 50% or another fraction).
5. Review the calculated travel‑day rate, the subtotals for full and travel days, and the total per diem allowance for the trip.
6. Optionally tweak the day counts or rate and rerun the calculation if your itinerary or policy changes.

Inputs explained

Per diem rate (full day)

The full daily allowance for meals and incidental expenses (M&IE) or total per diem, often set by your employer or government rates for the travel location. You can pull this from GSA, State Department, Defense Travel, or an internal policy document.

Full days

Number of full travel days where you are entitled to 100% of the per diem rate—typically days fully away from home, not counting departure/return if your policy uses reduced rates on those days.

Travel days

Number of arrival/departure days to which a reduced per diem rate applies (for example, 75% of the full‑day rate). Many policies count the first and last day of travel as reduced‑rate days, even if your flight times vary.

Travel day percent

The fraction of the full‑day rate that applies to travel days. A typical policy is 75% on arrival and departure days, but some organizations use 50% or another percentage. Enter whatever your employer, client, or reimbursement policy specifies.

Outputs explained

Full-day per diem

The full per diem rate you entered, shown as a currency amount. This is the baseline daily allowance for days where you qualify for 100% per diem.

Travel-day per diem

The reduced per diem rate for travel days, computed as full‑day rate × (travel‑day percent ÷ 100). This is the amount you can claim on days where policy allows only a fraction of the full rate.

Full-day subtotal

Total per diem allocated to full days: full‑day rate × number of full days. This is the portion of the allowance tied to days with 100% per diem.

Travel-day subtotal

Total per diem allocated to travel days: travel‑day rate × number of travel days. This highlights how much of the total comes from reduced‑rate days.

Total per diem

The sum of the full‑day and travel‑day subtotals. This is the overall per diem allowance for the trip under the rate and percentages you entered.

When to use it

• Estimating per diem for work travel reimbursements before you book or submit an expense report.
• Budgeting trip allowances when applying the 75% travel‑day rule so you know how much you can reasonably spend on meals and incidentals.
• Checking employer or client per diem totals against your own calculations, helping you catch mismatches or misunderstandings before they become a problem.
• Planning personal travel budgets when you want to simulate an M&IE allowance structure similar to a corporate or government per diem policy.
• Helping managers or finance teams validate per diem policy changes (for example, moving from 50% to 75% travel‑day rates) by modeling trip‑by‑trip impact.
• Training new employees on how per diem works by walking through concrete examples with their actual destinations and rates.

Tips & cautions

• Update the rate if you know the local GSA or other official per diem for your destination; using generic rates can under‑ or over‑estimate your allowance.
• Set travel days to 0 if all days are treated as full per diem under your specific policy.
• Keep records of which days are full vs travel days in your expense documentation so they match this calculation and your approver’s expectations.
• If your trip spans multiple locations with different per diem rates, run separate calculations for each location segment and add the totals together.
• When in doubt about how your employer handles partial travel days, check the written travel policy or ask your finance/HR team before relying on a particular percentage.
• Does not fetch location‑specific per diem tables; you must enter your own rate manually.
• Applies a single full‑day rate and a single travel‑day percentage across the whole trip; it does not handle changing rates by location or date in a single run.
• Does not distinguish between lodging and M&IE components of per diem; it assumes a single combined rate for simplicity.
• Ignores tax treatment of per diem and any employer‑specific caps or adjustments beyond the basic rate and travel‑day percentage.

Worked examples

Deep dive

FAQs

Does this calculator use official GSA or IRS rates?

No. You must enter the applicable per diem rate yourself based on your employer’s policy or official tables for your travel destination. This keeps the tool flexible for both government and private‑sector policies.

Can I use different rates for different days or locations?

This simple calculator uses one full‑day rate and one travel‑day percentage for the whole run. If your rate changes by location or date, run separate calculations for each segment of the trip and add the totals together.

Does this handle lodging vs M&IE separately?

No. It treats the per diem as a single combined rate. If your policy splits lodging and M&IE, you can run the calculator on just the M&IE portion or on a combined rate you derive yourself.

Is per diem always tax‑free?

Not necessarily. Tax treatment depends on whether your employer has an accountable plan and whether you substantiate travel. This calculator only helps you compute amounts; it does not determine whether per diem is taxable. Check with your employer or a tax professional.

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