Calculate the cost of client meetings.
A meeting's cost is person-hours times the charge-out rate, and the person multiplier is what makes it large: an hour with five people at 85 is 425 before anyone has prepared. Preparation is counted separately and per person, because it is real billable time that never appears on the calendar. The cost-per-minute figure is the useful one to keep in mind — at these numbers every minute of overrun costs about nine, which is what justifies an agenda and a hard stop.
Meeting cost
Cost = attendees x minutes / 60 x hourly rate
With preparation
Total per meeting = meeting cost + attendees x preparation minutes / 60 x hourly rate
Charge-out rate if the time is billable or displaces billable work, since that is the revenue forgone. Fully loaded salary cost is the right figure for internal meetings that displace nothing.
Remove attendees before removing minutes — cost scales linearly with headcount, and most meetings carry people who only need the outcome. Halving the attendance saves more than trimming fifteen minutes.