When it comes to protecting your boat, few accessories are as essential as boat fenders. Designed to absorb impact and prevent damage when mooring or rafting up, fenders are an affordable investment that can save you from costly repairs. But with so many sizes and styles available, it can be difficult to know which fender is right for your vessel.
In this comprehensive guide, we’ll walk you through the basics of boat fender sizing, explain what affects your choice, and provide a simple chart to help you match the correct size to your boat. Whether you’re a seasoned skipper or just getting started, this guide will help you get it right the first time.
Why Fender Size Matters
Choosing the wrong size fender can lead to insufficient protection. A fender that’s too small won’t absorb the force of impact, while a fender that’s too large may be cumbersome and unnecessary. The ideal size offers a balance between protection and practicality.
Key factors influencing fender size:
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Length and weight of your boat
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Mooring conditions (calm marina vs tidal dock)
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Boat type and hull shape
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Frequency of use and rafting up
General Guidelines for Boat Fender Sizing
A widely accepted rule of thumb is:
One inch of fender diameter for every 4 to 5 feet of boat length.
This is a starting point. For example, a 20-foot boat would typically use fenders that are about 4 to 5 inches in diameter.
Larger boats require more protection, and harsher mooring environments justify upsizing. Smaller boats used occasionally in calm conditions may be fine with more compact fenders.
Recommended Fender Sizes by Boat Length
Use the chart below to find a good starting point for your fender size:
| Boat Length | Fender Diameter | Fender Length | Quantity Recommended |
|---|---|---|---|
| Up to 10ft (3m) | 3" (7.5cm) | 10-12" (25-30cm) | 2-3 |
| 10-20ft (3-6m) | 4-5" (10-12.5cm) | 12-20" (30-50cm) | 3-4 |
| 20-30ft (6-9m) | 6-8" (15-20cm) | 20-25" (50-65cm) | 4-5 |
| 30-40ft (9-12m) | 8-10" (20-25cm) | 25-30" (65-75cm) | 5-6 |
| 40-50ft (12-15m) | 10-12" (25-30cm) | 30-35" (75-90cm) | 6-7 |
| 50ft+ (15m+) | 12"+ (30cm+) | 35"+ (90cm+) | 6+ |
Note: This is a general guide. Always consider your specific mooring conditions and consult your boat’s manufacturer or marina manager if unsure.
Popular Fender Types to Consider
At Morgan Marine Chandlery, we stock a wide range of fenders to suit every boat and budget:
Cylindrical (or sausage) Fenders
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Most common type
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Suitable for most motorboats and yachts
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Can be hung vertically or horizontally
Ball (or round) Fenders
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Offer more surface contact
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Ideal for larger, heavier boats or rougher moorings
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Also useful as a bow fender
Flat Fenders / Pad Fenders
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Good for tight spaces or narrow walkways
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Stackable and easy to stow
Bow and Stern Fenders
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Specially shaped for additional protection at key points
All these fenders come in a range of sizes and colours, and we also stock fender lines, fender covers, and inflation accessories to keep your setup looking smart and performing well.
Tips for Fender Placement
Having the right size is only part of the equation - placement matters too:
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Hang fenders so the bottom just touches the waterline
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Space them evenly along the hull where contact may occur
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Use more fenders when rafting up with other boats
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Adjust heights if mooring alongside a higher or lower quay
Keeping Your Fenders in Top Condition
To extend the life of your fenders:
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Rinse with fresh water after saltwater use
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Clean regularly with mild soap
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Store out of direct sunlight when not in use
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Use fender covers to prevent scuffing and UV damage
Need to upgrade? Our online chandlery makes it easy to browse top brands and fasten everything you need for a secure mooring setup.
Shop Boat Fenders Online with Fast UK Delivery
At Morgan Marine Chandlery, we offer a carefully selected range of high-quality boat fenders, fender lines, and covers - all with fast UK delivery.
Visit our fender collection today to find the right size and style for your vessel and keep your boat protected season after season.
Morgan Marine Chandlery – Trusted by UK boaters for quality marine gear and expert advice.
