Boat Dock Lines

A good rule of thumb is:

• 3/8” diameter lines for boats up to 25 feet
• 1/2” diameter lines for boats 25–35 feet
• 5/8” diameter lines for boats 35–45 feet
• 3/4” diameter lines for boats over 45 feet

Larger boats may require even thicker lines for extra security. For more information on dock line sizing, see our Dock Line Size Guide.

Dock lines are typically 1.5 to 2 times the length of your boat. For example, a 30-foot boat should have 40–60 foot lines for the bow and stern, and shorter spring lines of about the boat’s length (30 feet).

At a minimum, you’ll need four dock lines—two bow/stern lines and two spring lines. This setup keeps your boat secure and helps prevent forward, backward, and sideways movement at the dock.

Dock lines should be snug but not overly tight. You want enough slack to allow your boat to rise and fall with tides and waves, but not so much that the boat shifts excessively or bangs into the dock.

The best dock lines are made from nylon because it combines strength, stretch, and durability. Nylon absorbs shock from waves and wind better than polyester or polypropylene, helping protect your boat and dock from damage.

The most common knots for dock lines are the cleat hitch, bowline knot, and clove hitch. These knots are secure, easy to tie, and just as easy to release when it’s time to leave the dock. To learn these knots, see our resource: How to Tie Dock Lines

Most boats have cleats, bollards, or pad eyes specifically for securing dock lines. Run the line through or around the dock’s cleat or piling, then tie it off to your boat’s cleat using a cleat hitch or bowline knot.

Yes—sun, saltwater, and constant strain can weaken dock lines over time. Inspect your lines regularly for fraying, stiffness, or UV damage, and replace them if they show signs of wear.

Color is mostly personal preference, but darker colors like black tend to show less dirt and UV damage, while white or blue can look cleaner and more traditional.

It’s not recommended. Dock lines are specifically designed for boating, with spliced eyelets and marine-grade nylon that resists sun, salt, and abrasion. Ordinary rope won’t perform as well or last as long.