Enter your trip and rates — get the total with travel-day proration, and what modest spending pockets.
Trip per diem total
—
| Full days | — |
| Travel days (prorated) | — |
| At your spend rate, you'd pocket | — |
Meals & incidentals math — lodging is usually booked/reimbursed separately at actual cost.
The per diem math
total = (full days × rate) + (2 travel days × rate × 75%)
Simple by design — that's per diem's whole pitch: nobody itemizes a sandwich. The proration exists because departure-day breakfast at home shouldn't bill like a client-dinner Tuesday, and 75% was the compromise everyone standardized on.
A worked example
A 4-day trip at $68 M&IE: two full days ($136) plus two travel days at $51 each — $238 total. Spending a realistic $45/day leaves about $58 in your pocket, tax-free. Frequent travelers who eat sensibly bank four figures a year this way; it's the closest thing corporate travel has to a legal perk.
Per diem vs expense reports
Per diem trades ceiling for freedom: no receipts, no arguing over a $19 airport salad, keep the difference. Actual-expense policies reimburse more for genuinely expensive trips but pay nothing for thrift. If you're on the receipts system instead, our expense tracker is the companion tool — and either way, mileage rides on top (that calculator).
Frequently asked questions
How does per diem work?
A flat daily allowance for meals and incidentals (and sometimes lodging) instead of collecting receipts. Within federal GSA rates it's tax-free; your employer sets the actual rate, often pegged to the GSA table for your destination.
What is the 75% first and last day rule?
Travel days aren't full days, so standard practice (and the federal rule) pays 75% of the meals rate on the day you leave and the day you return, regardless of departure time.
Do I get to keep unspent per diem?
Under most flat per-diem policies, yes — that's the deal's quiet feature: eat modestly and the difference is yours, tax-free. Policies requiring receipts against the allowance are reimbursement plans wearing a per-diem name; know which you have.
Where do I find the per diem rate for my city?
GSA.gov publishes rates by county/city (updated each October) — a standard rate for most places and higher rates for expensive metros. Your travel policy will say whether it follows GSA or sets its own.