It is important to note, that not all yarn weights are created equal between brands, or even within the same brand. For example, you may have a yarn labeled 4 (worsted weight) in one brand that is not congruent with another 4 (worsted weight) in another brand. This is why it is critical to check gauge when following a pattern, especially when making a wearable garment. Missing the step of ensuring gauge is correct, can easily result in a project turning out too large or too small. For more information on gauge, check out this blog post.