What Size Fenders do I Need for My Boat? - Boat Fender Size Chart
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It goes without saying that protecting the hull from damage is a top priority for boaters. When sized correctly, boat fenders provide necessary cushioning against damage caused by docks and other boats. But what happens when the fenders used are too big or too small for the vessel they’re protecting? Too small of a boat fender won’t protect the hull and can even burst on impact, while boat bumpers that are too large can be cumbersome and inconvenient to store onboard. In this post, we take the guesswork out of determining the correct fender size for your boat with our easy-to-read boat fender size chart.
Boat Fender Size Chart by Boat Length
| Boat Length | Cylindrical Fender Diameter | Round Fender Diameter | Flat Fender Size |
| Under 10' | 3" | n/a | Small |
| 10' - 15' | 3" - 4" | 9" | Small |
| 15' - 20' | 5" - 5 1/2" | 12" | Small |
| 20' - 25' | 6" - 6 1/2" | 15" | Medium |
| 25' - 35' | 8" - 8 1/2" | 18" | Medium |
| 35' - 50' | 10 1/2" - 12" | 21" | Large |
| 50' - 60' | 12" | 27" | Large |
| 60' - 72' | 15" - 24" | 27" | Large |
Pro Tip: When choosing the right size fender, a cylindrical fender should have one inch of diameter for every four to five feet of boat length and two inches for a round fender. The larger a vessel is, the heavier it tends to be. With more weight behind the impact, larger boats need larger, more durable boat fenders to adequately safeguard the hull.
Choosing a Fender Type
Now you know what size boat fender you need, but what about the style that is best for your vessel? Not all fenders for boats are created equal. Let’s explore what fenders will provide the best possible protection for your boat based on its length.
Fenders for Small Boats (<15' - 20')
For smaller boats such as a personal watercraft or row boat, a classic utility fender with smooth sidewalls will provide economical protection upon impact with docks or other vessels. These fenders often feature an oval shape that keeps them from rolling out of position while minimizing hull rub.
Fenders for Medium-Size Boats (20' - 35')
There are a wide range of boat fenders that suit medium-size boats. Whether you’re skippering a cuddy cabin or cruising in a bow rider, you’ll want to safeguard your ship with fenders that feature ribbed sidewalls to minimize roll and either reinforced eyelets or a center rope tube design for hanging horizontally.
Fenders for Large Boats (35' - 75')
Big boats require big protection. Large fishing boats, cabin cruisers and yachts require deep hull protection that only commercial-grade boat fenders can provide. Designed to withstand the toughest marine conditions, these boat bumpers feature durable, seamless construction and extra-large line holes to accommodate heavy-duty ropes and shackles. You may even want to opt for fender cushions, which feature multiple attachment points and enhanced crush resistance.
How Many Fenders Do I need?
No matter what style of boat fenders you choose, a good rule of thumb is to have one boat bumper for every 10 ft. of waterline per side, with a minimum of three for even the smallest boats.
| Boat Length | Recommended Number of Fenders Per Side |
| Under 10' | 3 |
| 10' - 15' | 3 |
| 15' - 20' | 3 |
| 20' - 25' | 3 |
| 25' - 35' | 4 |
| 35' - 50' | 5 |
| 50' - 60' | 6 |
| 60' - 72' | 7 |
Boat Fender Accessories
Keeping your boat fenders in good condition is essential to getting the maximum return on your investment. Consider outfitting them with boat fender covers that are designed to fit snugly and protect your fenders from building up dirt and grime.
From fender lines, adjusters and cleats that you can use to hang fenders to racks that you can use to store them, Lippert stocks a wide range of boat fender accessories to make docking, mooring and rafting easier.
