The weight of a sweater is probably the most useful and least communicated piece of information in all of clothing. It describes how the garment will perform much better than its composition does.
Ultralight. Extremely thin, almost devoid of volume. It is the weight for wearing under a jacket, for travel, and for layering.
Beware of a misconception: ultralight does not mean fragile or poor quality. A very light garment often requires more precision in construction than a heavy one, because every irregularity shows and stability must be achieved without excess material.
Light. Worn on its own during transitional seasons and under a jacket in winter. It is the most versatile weight and the one usually worn the most days of the year.
Medium. The sweater as one imagines it: it holds its shape, has presence, and provides warmth without becoming bulky. Autumn and winter in the city.
Warm. Full constructions, often with stitches that add thickness. It is the garment for real cold, and it makes sense to buy it knowing that it will stay in the closet for eight months.
However, there are two important caveats.
The first: weight cannot be deduced from composition. There are pure ultralight cashmeres and warm blends, and anyone who claims otherwise is oversimplifying.
The second: thermal perception is personal. Some people are fine in the office with a light weight in December, while others are cold with a medium weight in October.
That is why we avoid associating weights with precise temperatures: it would be a promise that no garment can keep.
The practical criterion that works best is to think about what you will be wearing along with the garment. Layering changes the response more than the season.
