“There's a waiting list” is the least useful sentence a harbourmaster says. The number people actually want is years, and it comes from two facts the marina already has: how many slips of that size exist, and how many of them turn over in a normal year. Everything else is arithmetic.
96 names on a list for 120 slips that turn over at 8% a year is 9.6 openings annually — a ten-year wait.
The example
Three slip categories at the same marina, with very different waits.
| A | B | C | D | E | F | |
|---|---|---|---|---|---|---|
| 1 | Slip type | Waitlist | Slips | Turnover | Openings/yr | Years to reach |
| 2 | 40 ft open | 96 | 120 | 8% | 9.6 | 10.0 |
| 3 | 30 ft open | 45 | 150 | 12% | 18.0 | 2.5 |
| 4 | Covered slip | 62 | 40 | 5% | 2.0 | 31.0 |
The formula
Openings deserves its own column because it is the number nobody has calculated:
How it works
Two facts and one division:
C2*D2is openings per year. Turnover is the share of slips that change hands annually — boats sold, tenants moving, upgrades to a bigger slip. Pull it from three years of history, not from a guess.B2/E2is the wait in years for someone joining the list today. A person already at position 12 waits12/E2instead, which is a much friendlier number to quote on the phone.- Round to one decimal. Quoting “10 years” from a 9.63 calculation is fine; quoting 9.63 implies a precision the turnover rate cannot support.
- Run it per slip size. A marina with a two-year wait for 30-footers and a thirty-year wait for covered slips does not have “a waitlist” — it has two completely different businesses.
Covered and oversized slips are almost always the extreme cases. If one category is running past twenty years, the honest move is to close the list rather than keep collecting deposits against it.
Try it: interactive demo
Enter the waitlist length, the number of slips and your annual turnover rate.
Variations
Wait from a specific position
Divide the position rather than the whole list. This is what the person on the phone is actually asking.
List length that means a five-year wait
Solve backwards to find the cut-off. Once the list is longer than this, stop adding names.
Pitfalls & errors
Waitlist attrition is real and it works in the applicant's favour. Perhaps a third of names decline when the call comes, which shortens the effective queue — if you track decline rate, divide the list by (1-DeclineRate) before the wait calculation.
Turnover is not stable across a cycle. Fuel prices, a hot used-boat market, and a marina rate increase all move it, so recompute annually rather than treating the rate as a constant.
Do not use total marina slips for a size-specific list. A 30-foot boat cannot take a 40-foot slip at a 30-foot price, so each category has to be sized against its own inventory.
Practice workbook
Frequently asked questions
How do I measure turnover if I have never tracked it?
Should I charge to be on the waitlist?
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