Carbon Fiber K Grades Explained

Seeing “3K” or “12K” in an advertisement can make a buyer scratch their head with confusion. Let’s have a closer look into the meaning of K.

About K

You have probably heard about 3K and 12K carbon fiber. In addition to that, there are 1K, 2K, 6K, 24K and so on. To understand them better, let’s have a deeper look into how carbon fiber plates are made.


Carbon fiber is supplied in the form of a continuous tow wound onto a reel. The tow is a bundle of thousands of continuous individual carbon filaments, held together and protected by an organic coating.

Carbon Fiber tows

Let`s expound the main factor. 12K means there are 12,000 filaments per “tow”, 3K means there are 3000. The tow is made convenient for unwinding it from the reel. Each carbon filament in the tow is a continuous cylinder. Filaments are in diameters between 5–8 micrometers and they consist almost exclusively of carbon.

1K Carbon Fiber

1K carbon fiber is a rare find. It is lighter than other fibers and provides more smoothness than a larger weave. 1K fiber is exclusive and rather expensive. Low modulus fibers are better as a finishing surface. 22,568 ft/lbs, 66 g/m2

2K Carbon Fiber

2K carbon fiber is the rarest carbon fiber on the market. It is produced by no more than 2 carbon manufacturers in the world. The plate has perfect stiffness, low weight and great vertical compliance (comfort). It is as well on the expensive side of carbon fibers.

3K Carbon Fiber

3K carbon fiber is the most popular, most common carbon fiber. The plate has a classic carbon fiber look. 3K is the workhorse of carbon fiber. It’s light, relatively stiff, easy to find and simple to use. 3K has higher elongation to failure and a better strength than 6K, 9K or 12K. As 3K has a smaller bundle of fibers, thinner fabric and filament wound tubes can be produced. If fibers are the same grade, stiffness and strength, they are not affected by the tow size. 3K carbon fiber is used in aviation, industrial field, architecture, sporting, recreation goods. 7,523 ft/lbs, 198 g/m2

6K Carbon Fiber

6K and 9K carbon fibers are smoother to work with than 12K fibers. Fibers wet out easier and drape better. Used in aerospace, building reinforcement, car tuning .7,523 ft/lbs, 396 g/m2

12K Carbon Fiber

12K carbon fiber is cheaper than the others. Many factories use this fabric to keep their costs low. 12K is easier and cheaper to produce as it only takes 1 layer instead of 3. 12K fibers are not always preferred, as they have a big and robust look. By definition, the larger the weave, the stiffer and heavier it is. 12K carbon fiber has higher tensile strength. It is used from military to industrial robotics for scientific equipment. A layer or two is used in critical high-stress areas like the BB area, HT area and the chainstays. 1,862 ft/lbs, 800 g/m2

24K & 48K Carbon Fiber

24K and 48K carbon fibers are used for manufacturing filters, heat protection, working clothes, pipes and industrial details.

Unidirectional Carbon Fiber

Unidirectional carbon fiber has fibers that run the same direction rather than being woven together. This type of carbon fiber can be used for carbon bicycles. It is also used in airplane wing spars, running along the length of the wing, where strength and stiffness are needed.

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