What's the difference between 150, 175, and 250 weight merino?

The numbers refer to grams per square meter of fabric. According to r/Skigear discussion, 250-weight is roughly 1.5x thicker than 150-weight, with noticeably more warmth and wind resistance. 150-175 weight is generally recommended as a three-season or high-output layer, while 250 is winter-specific and can feel like overkill above freezing per outdoorgearlab.com testing notes.