The airfare line of an offsite budget is one multiplication per departure airport: the cheapest direct round-trip to a candidate city, times the number of people flying from that airport, summed across airports and then padded. Built that way it takes a few minutes instead of two weeks of tab-by-tab searching, and it prices three or four candidate cities in the same pass.
The sections below give the arithmetic, the two things that move the total most, what changes for an international destination, and what the estimate deliberately leaves out.
The method
Step 1. Headcount per airport. From the roster: how many people fly from each origin? A 20-person team might be SFO ×6, JFK ×5, ORD ×4, AUS ×3, DEN ×2. This table is 80% of the work and you build it once per planning cycle.
Step 2. The intersection, with prices. Enter those airports in Midway. Every destination in the results is nonstop from all your origins, and the table carries the cheapest direct round-trip per origin for each destination, which is the per-seat number you would otherwise open fifteen tabs to collect. Those prices come from Kayak’s search data, so a low-traffic destination can come back without one, in which case a live Kayak search is one click away. (Midway earns a commission on flights booked through those links.)
Step 3. Multiply. For each candidate destination, sum the cheapest fare per origin times the headcount at that origin. For the 20-person team above, a Denver offsite prices out as 6×$250 + 5×$320 + 4×$210 + 3×$280 + 2×$0-ish (they drive), or about $4,800.
Step 4. Buffer. Multiply by 1.3. The cheapest fare is a floor rather than a forecast: your dates are fixed, some people book late, some need the 9am instead of the 6am, and refundable corporate fares carry a premium. Thirty percent over the cheapest-fare baseline is the honest planning number, which puts Denver at roughly $6,200 in airfare for 20 people.
Run the same arithmetic down two or three candidate cities while the table is open. Once the headcount table exists, comparing destinations costs nothing.
What a connection adds to the fare
Domestic nonstop round-trips mostly land in the $200–500 band. A connection typically adds 30–80% to the fare, plus four to six hours of travel time per person each way. It is the largest lever in offsite airfare, larger than booking class and larger than season.
If 8 of your 20 people need a connection to reach a destination that fails the nonstop test, that is roughly $1,500–3,500 of extra airfare and around 60 person-hours in airports, which you paid for in salary and in day-one energy even though no invoice says so. Starting from the nonstop intersection rather than from a destination wishlist holds that cost at zero for every city the method prices.
When full coverage is not possible, for the colleague in Boise or the teammate in Berlin, price their itineraries individually and add them as explicit line items. Two known connections chosen deliberately are a budgeting detail. Twelve discovered at booking time are a budget overrun. The roster-to-shortlist method covers how to decide who connects.
Booking window and day of week
The per-seat floor you pulled is a snapshot and it decays. Fares on popular offsite routes climb sharply inside six weeks of departure. The offsite pillar guide recommends locking flights 8–12 weeks out domestically and 12–16 weeks internationally, and hitting that window usually saves more than any other adjustment on this page.
Day of week matters almost as much for an offsite, because everyone travels on the same days. A Tuesday-to-Friday offsite books cheaper, flight by flight, than Thursday-to-Sunday, and midweek room blocks are cheaper too. If leadership is flexible on the pattern, run the estimate both ways. A two-day shift is often worth 15–20% of the whole flight line.
Adjusting the method for an international city
The method survives contact with an international destination and only the constants change. The flight line roughly doubles: a $350 domestic average becomes $700–900 for Europe, somewhat less for Mexico and the Caribbean. The buffer should grow from 30% to about 40%, because international fares move more and rebooking costs more when someone’s plans change.
Two line items appear that a domestic estimate does not have. Add a night of hotel for any destination more than three time zones away, since day one after an eastbound red-eye is a half-day whether or not the budget says so. Then add a passport-and-visa contingency: in any 30-person US team, assume at least one expedited passport renewal at around $200. The international offsite guide covers which destinations keep these adjustments small, Mexico City and Toronto barely move the constants and Lisbon moves all of them.
What the estimate leaves out
Knowing what the number excludes keeps it defensible. It ignores seat class, so if your travel policy upgrades long-haul flights, apply that policy’s multiplier yourself. It ignores the origin-fairness question, reimbursing actuals against a flat cap, because the total is the same either way and only who absorbs the variance changes (that policy choice is covered in the pillar’s logistics playbook). And it ignores ground transport, which belongs in the hotel-and-venue bucket.
It also uses the cheapest direct fare rather than an average fare as its base. That is what makes the comparison between destinations honest: every candidate city is priced by the same rule, so the ranking holds even when the absolute numbers drift. The buffer absorbs the drift and the ranking drives the decision.
From estimate to slide
The deliverable this method produces, formatted for the meeting where it matters:
| Destination | Airfare (20 ppl, buffered) | Nonstop coverage | Worst flight |
|---|---|---|---|
| Denver | ~$6,200 | 20/20 | JFK, 4h17 |
| Nashville | ~$7,100 | 20/20 | SFO, 4h33 |
| San Diego | ~$8,300 | 18/20 | BOS, 6h12 |
Add hotel, venue and meals, roughly $700 per person for a two-night domestic offsite per the pillar’s budget breakdown, and every city on the slide carries a full per-person cost next to it.
Fares drift between the estimate and the booking and the ranking drifts far less, so re-pull the numbers before anyone books rather than trusting a total from three months earlier. The cluster hub has the destination-finding side of the process.
Price two or three candidate cities against your own roster.