Every office landlord knows retention matters. Far fewer have put a number on it, and the number changes behavior, because the gap between what a renewal costs and what a replacement costs in office is not a margin. It is a multiple, and once you have computed it for a specific suite, several leasing decisions that felt like judgment calls become arithmetic.
Price the two paths side by side. The renewal path: a refresh allowance, a smaller commission, maybe a month of free rent as a courtesy, and the rent continues without interruption. The replacement path: the suite goes dark for the downtime office is famous for, the new tenant's improvement package runs to a number that would have sounded fictional a decade ago, the free rent stacks on top, the full commission lands, and the building carries the suite's expenses the entire time. On typical suburban office numbers, the replacement path costs several times the renewal path before the new tenant has paid a single full month, and on longer downtimes the multiple gets uncomfortable to say out loud.
That multiple has a strategic conversion, and it is the useful part: it tells you exactly how much rent you can concede at renewal and still come out ahead. If replacing the tenant costs the equivalent of eighteen months of rent and renewing costs four, the breakeven concession is enormous, far larger than the bump-versus-market debate that usually dominates the renewal conversation. Landlords lose good tenants over rent differences that are a fraction of the replacement cost they trigger, because the replacement cost was never on the table when the negotiation happened. Put it on the table. Your own table, at minimum.
The widget below runs the comparison for one suite: your renewal package against your honest replacement package, and it returns the cost gap plus the breakeven rent concession that gap funds. Two honesty notes for using it. Downtime is the input people shade, so use what suites like this one actually take in this submarket, not what the leasing plan hopes. And the renewal is never certain, which is the widget's boundary: the real decision weights both paths by the tenant's actual renewal odds, which turns this from a comparison into an expected-cost problem.
That expected-cost problem, run across every suite and every expiration in the hold, is what office underwriting actually is, and it is what PropCalc™ models natively: per-tenant renewal probability, downtime, TI, free rent, and commissions, priced through the full pro forma so the rent roll's turnover economics stop being folklore. The suite-level math on this page is the intuition. The building-level version is the deal.