Takeoff suggested bow, stern, breast, and spring line lengths from overall boat length (LOA). Based on common recreational rules of thumb — not a marina contract.
Common recreational guidance (including West Marine’s dock-line advisor): bow and stern lines about ⅔ of LOA, breast lines about ½ LOA, spring lines about 1 × LOA.
bow/stern ≈ 0.67 × LOA
breast ≈ 0.50 × LOA
spring ≈ 1.00 × LOA
Diameter rule of thumb often cited: ~⅛″ diameter per 9′ of boat length (step up for heavy displacement or exposed berths).
Tidal slips, high freeboard, and exposed docks may need longer or thicker lines. Nylon three-strand is the usual stretchy choice for dock lines. This page sizes length takeoff only. Volume/KD: unknown.
| Approx LOA | Common nylon dia. (guide) |
|---|---|
| Up to ~27 ft | 3/8″ |
| ~28–31 ft | 7/16″–1/2″ |
| ~32–36 ft | 1/2″–5/8″ |
| ~37–45 ft | 5/8″–3/4″ |
A minimum transient set is often bow, stern, and two springs (four). Permanent berths commonly use six or more. This takeoff lists lengths; you choose how many to buy.
Springs control fore-aft surge. A line about as long as the boat gives useful geometry between cleats without being so short it snatches.
High freeboard and large tidal range can call for longer working lengths than the ⅔ rule. Treat these numbers as a shopping start, then measure your slip.
Nylon stretches and absorbs surge — the usual dock-line choice. Polyester stretches less and is better when you want less bounce. Avoid polypropylene for primary dock lines; it floats but UV and abrasion wear it out faster.