What Size Surf Fins Do I Need?

Fins were first added to surfboards nearly a century ago and they remain an essential part of its construction, providing more drive and control for the surfer.

But with so many different fins of varying sizes, how do you know which size is right for you?

How Fins are Added

Fins are either removable or “glassed-in”.

Glassed-in fins are attached to the board with fiberglass and they cannot be removed. They tend to be smoother and stronger and they provide greater overall strength.

However, they are difficult to repair and don’t afford you the sort of versatility that you get from removable fins.

As the name suggests, a removable fin is one that can be removed, which means you can repair it easily or swap it if required. Removable fins are screwed into a fin box and can be adjusted as needed.

Start with Your Weight

When choosing the right fins for you, start with your weight:

  • Fin Size Grom = Under 100 lbs.
  • Fin Size XS = Under 120 lbs.
  • Fin Size S = 105 to 155 lbs.
  • Fin Size M = 145 to 195 lbs.
  • Fin Size L = 165+ lbs.
  • Fin Size XL = 190+ lbs.

If your weight is in one of the overlapping groups, you can choose from either of the two sizes, focusing instead on the material of the fin or the quality of the board.

Choosing your Configuration

Once you know the size, it’s time to choose the right configuration.

Check the bottom of your board for between 1 and 5 spaces to indicate whether it’s a Single, Twin, Thruster/Tri, or Quad/Four. If there are 5 spaces, it means you have a little more freedom to mix and match.

Single Fins

Common on Longboards, the single fin setup is also the most traditional.

Single fins tend to be larger than the fins used on other setups and provide the sort of stability and control that beginners need. At the same time, however, single fins have very limited movement and are not the best for maneuverability.

Most Longboard fin boxes are long, so you can adjust where the fin is attached, bringing it forward to provide more ease when turning and moving it back to deliver more control.

Twin Fins

Twin fins are often fitted to Shortboards with a view to increasing speed and making the boards maneuverable, slick, and fun. They are not ideally suited for riding big waves but are great for most other types of surf.

3 Fin / Thruster

Thruster setups are very common these days and can be seen on all shapes and sizes of board. The fins are positioned in a “V” shape and the two outer fins are often angled inward.

A Thruster setup can be configured as a single fin or twin fins, and when left as a tri-fin it provides a great deal of stability, speed, and control.


Quad fins deliver high speeds and rapid acceleration in smaller surf and can also generate high speed while turning. There are two fins on either side of the board, and these are often angled slightly inward.

Other Surf Fins

The 2+1 setup is quite common and has its uses for Longboard surfers.

It contains three fins in the same positions as the Thruster. The difference is that the back fin is much larger, just like a single fin, and this provides a couple of configuration options that make the 2+1 ideal for beginners.

As noted above, there is also a 5 fin, although this is not intended to be ridden with all 5 fins and is simply there to create more possible configurations.