If you've ever tried to slide a surfboard into a cover and found it won't fit — even though the cover is technically the right length — you've run into the same problem we built Boardsox to solve. Length is the easy part. The real question is width and thickness together.
This guide explains why, gives you the one measurement that captures both, and walks you through our canvas and zipperless size charts.
Your three numbers
Every surfboard has three dimensions printed on the underside near the fins. You need all three — but for sizing a cover, two of them matter much more than the first.
Length
Nose to tail. For canvas covers we make every cover to your exact length. For zipperless, pick the closest size up.
Width
Across the widest point. This is the number that determines which cover style will fit.
Thickness
Through the middle. A thicker board takes up more room inside a flat-ish cover than most people expect.
Why width and thickness matter more than length
A surfboard is a three-dimensional object. A cover is essentially a flat bag. When you slide the board in, the cover has to wrap around the deck and the rails — which means thickness eats directly into the effective width.
Two boards that are both 6'0" and 21" wide can behave completely differently inside the same cover if one is 2¼" thick and the other is 2¾". The thicker one is genuinely bigger.
The number that counts isn't width on its own — it's width plus thickness, measured in one go.
Sarah Quinney, co-founderHow to measure rail to rail
Rail to rail is the single measurement that captures width and thickness together. Here's how to take it:
Rest the surfboard deck-up on a flat surface. Grab a soft tape measure.
Place one end of the tape on the middle of the left rail — not the very edge, the midpoint of the rail's curve.
Run the tape up and over the deck, across the widest and thickest point, down to the middle of the right rail.
Read the number. That's your rail-to-rail measurement. Match it to the charts below.
Canvas cover sizes
Our canvas covers are made to order — so length is never the issue. What we can't change is the cover's width:
- Shortboard canvas — under 22" (53 cm) rail to rail.
- Funboard canvas — up to 24" (58 cm) rail to rail.
- Longboard canvas — up to 25" (63 cm) rail to rail.
Over 25"? Get in touch with your dimensions and we'll look at a custom cover.
Zipperless cover sizes
Zipperless bags come in set sizes. The Easy Wing closure adds a few inches of length tolerance, but width is fixed per style:
- Shortboard zipperless — under 22" rail to rail.
- Fun & Fish zipperless — up to 24" rail to rail.
- Longboard zipperless — up to 26" rail to rail.
Between sizes on length? Always size up. The rolling closure takes up the slack.
Use our calculator
Plug your board's length, width and thickness into our size guide calculator and it'll tell you exactly which canvas style and zipperless size to grab.
