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What 500gsm Means

September 30, 2026 · 6 min read

On October 20, 2024, Boston woke up at 48 degrees. By the afternoon it was 77. You leave the house in a jacket, and by lunch you are carrying it. That is a New England fall, and spring is no different. It is the day a heavyweight piece is made for.

Heavyweight has a feel. The garment is made of something substantial. It is not a thin sheet of cheap material that gives up the first time the wind comes off the water. That feel has a number behind it, and the number is on every one of our heavyweight pieces: 500gsm.

What gsm means

Gsm stands for grams per square meter. Lay a flat square of fabric one meter on each side on a scale, and that is its gsm. It measures the cloth, not the finished garment, which makes it the fairest way to compare one sweatshirt to another.

500gsm works out to about 14.7 ounces per square yard. For a sense of scale, here is how it sits against other pieces we make:

You feel the difference before you read the label. The quarter zip alone weighs 32 ounces, by our supplier's count. That is two pounds of cotton.

What French terry is

French terry is a knit. The outside is smooth and flat. The inside is rows of small loops, left as they are.

Fleece starts the same way, then the loops are brushed until they break into a soft, fuzzy pile. That makes fleece warm, but it holds heat and moisture close. French terry keeps its loops whole. They pull moisture off the skin and leave channels for air to move. The result is warmth that breathes, and a surface that stays clean and flat after a lot of washing.

Put the weight and the knit together and you get the point of the whole thing. There is enough cloth to hold warmth at 48 degrees, and enough air moving through it that you are not cooking at 77.

Why weight matters here

I checked the numbers, because I wanted to know if the swing was as big as it feels. Across ten years of spring and fall days in Boston, Providence and Worcester, a typical day moves about 16 degrees from its low to its high. One day in ten moves 25 or more. A couple of times a season it moves 30. Now and then it moves about 40: Boston went from 49 to 88 on April 13, 2023, and Providence from 30 to 72 on March 11, 2021.

A thin sweatshirt handles the easy days. A heavyweight one handles the other kind. Zip the collar up on the walk in. Open it by noon. Take it off by two and carry it over your shoulder, and it still looks like something.

What ours are made of

The final step happens in Los Angeles or Philadelphia, where each piece is embroidered to order and shipped to you.

The heavyweight pieces

All four have an oversized, relaxed fit. It is built to go over a tee and under a coat.

Caring for heavyweight cotton

Frequently asked questions

Is 500gsm heavy for a sweatshirt?

Yes. It is close to twice the weight of our Links Quarter Zip, and the heaviest cloth we use.

Is French terry warm enough for winter?

As a layer, yes. On its own on a January day, no. It is built for fall and spring, and for going under a coat when it gets colder.

Will it shrink?

A little. It is pre-shrunk, and our supplier expects 0 to 3 percent after that. Wash cold and hang dry.

Heavy enough to hold the morning. Open enough for the afternoon. Built to still be in your closet in ten years.

Keep reading: Why Supima Cotton Matters · Modern New England Style

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