How to Measure Your Boat Fender for a Custom Cover

Why Measurements Matter More Than Brand Name

When most boaters think about ordering a custom fender cover, their first instinct is to look for the brand name stamped on the fender — Polyform, Taylor Made, Mission Sentry. But the brand name is actually the least important piece of information you need. What matters is the inflated dimensions: diameter and length.

Two fenders from completely different manufacturers can be identical in size and use the exact same cover template. A generic offshore fender and a Polyform F-Series can share the same diameter and length — and Flexifabrics engineers covers from the actual dimensions, not the label on the rubber. This is why customers with off-brand, store-brand, or unbranded fenders get the same precision fit as anyone buying Polyform fender covers or Taylor Made fender covers.

The brand tells you the shape family. The measurements tell us how to cut your cover. Always start with the measurements.

What You Need to Measure

A soft tape measure — the kind used in sewing — or a piece of string and a ruler. That's it. You do not need calipers, gauges, or any specialized tool. Two measurements, two minutes, and you have everything needed to engineer a precision cover for your exact fender.

How to Measure Fender Length

Length is the measurement from tip to tip along the longest axis of the fender — the full end-to-end span when the fender is held vertically or horizontally at full inflation.

Run your tape measure from the very end of one tip to the very end of the other. Do not measure the body of the fender only — include the tapered ends.

How to Measure Fender Diameter

Diameter is measured across the widest point of the fender — the full width at its fattest cross-section when fully inflated.

For cylindrical fenders (the most common type, like Polyform F-Series and G-Series), the widest point is the center of the fender. Place your tape measure across the middle and read the straight-line distance from one side to the other.

For spherical or ball-style fenders (like Polyform A-Series), the diameter is consistent across any equatorial cross-section. Simply measure straight across the middle from any angle.

What to Do If You're Between Sizes

Sometimes a fender falls between two standard dieline sizes — your diameter reads 8.8 inches and the two nearest templates are 8.5 and 9.5. In this case, always round up to the larger size.

A cover that is slightly looser fits cleanly and slips on easily without stress. A cover cut to a size that is too tight places excessive strain on the neoprene seams over time — accelerating wear and risking a seam failure that voids the warranty. When in doubt, go larger.

Common Fender Sizes Quick Reference

If you're not sure where your fender falls, this quick reference by vessel size will point you in the right direction. These are typical ranges — always confirm with your own measurements.

Submit Your Measurements to Flexifabrics

Once you have your diameter and length, submitting your order is straightforward. Through our custom request form, you provide your measurements, quantity, and any design direction — boat name, colors, logo, or just a general style preference.

From there, our team engineers your exact dieline from the submitted dimensions. Within 24–48 hours you receive a free digital mockup showing your cover on a rendering of your exact fender type, with your design applied exactly as specified.

No payment is collected until you approve every detail of the design and confirm you're satisfied with the mockup. Revisions are unlimited — we won't move to production until the cover looks exactly the way you want it.