What Size Vest Do I Need Over a Sweater?

Most men order a vest one size too big for layering. Counted across all 25 vests in the Adam & Westcott range, here is the size you can actually get.
Last updated: September 2026

What size vest do I need over a sweater?

Stay in your normal size over a thin knit, and go up one size only over a thick one. Across the 25 active Adam & Westcott vests, every single one carries M, L, XL and 2XL, so that size up is available on 100 percent of the range.

A vest is the one layer where sizing up is usually unnecessary. With no sleeves and no cuffs, the only bulk it has to clear is across your chest and back. A merino knit adds almost nothing there. A heavy rib or a cable knit does, and that is where the next size up earns its place.

Your usual size	Over a thin knit	Over a thick knit	Vests offering that size up
S	S	M	21 of 21 (100%)
M	M	L	25 of 25 (100%)
L	L	XL	25 of 25 (100%)
XL	XL	2XL	25 of 25 (100%)
2XL	2XL	3XL	21 of 25 (84%)
3XL	3XL	4XL	12 of 21 (57%)
4XL	4XL	5XL	6 of 12 (50%)

Do you always size up a vest for layering?

No. Size up only when the sweater underneath is a heavy knit. With no sleeve to bind at the armhole, a vest sits over a knit at its true size and still zips cleanly. Size up over a thin layer and you get a vest that gapes at the armhole and rides up when you reach.

Two knits from the Adam & Westcott range show the split. A Merino Wool Sweater at $114.98 is a true-size layer, so keep the vest at your normal size. A Heavy Rib Sweater at $44.99 or the Thick Knit Cashmere Sweater at $119.99 is the case for the next size up.

Which Adam & Westcott vests still have room above 2XL?

21 of the 25 vests run to 3XL, but only 12 reach 4XL and just 5 reach 6XL, so a 2XL wearer should check the run before counting on a size up. Four vests stop at 2XL, which means a 2XL buyer who wants layering room has nowhere to go on those four:

• Layered Hood Vest, $59.98, S to 2XL
• Lapel Collar Vest, $49.99, S to 2XL
• Hooded Puffer Vest, $49.99, S to 2XL

The practical move for a 2XL buyer who layers over heavy knits is to start from a long run instead. The Packable Down Vest carries 10 sizes from XS to 6XL, the longest run in the collection.

What if you wear XS or S?

21 of the 25 vests carry S, but only 10 carry XS and a single vest carries XXS, so a smaller frame has roughly a third of the range to choose from. Four vests start at M with no S at all. If you wear S and want a vest that sits close over a thin knit rather than swimming on you, filter to the runs that begin at XS.

The one vest in the collection that starts at XXS is the Duck Down Vest at $59.98, running XXS to 4XL across 9 sizes.

Which vest handles the thickest sweaters?

The Packable Down Vest at $69.98 is the pick for heavy knits, filled with ninety percent duck down and offered in all 10 sizes from XS to 6XL.

For a thinner layer that sits under a coat, the Softshell Fleece Vest at $39.98 runs S to 6XL across 9 sizes, and the Heather Fleece Vest at $59.98 covers XS to 3XL. If you want pockets and a reversible build over a knit, the Multi-Pocket Cargo Vest at $59.99 runs S to 6XL.

Frequently asked questions

Should I size up a vest to wear over a sweater?
Only over a heavy knit. A vest has no sleeves, so a thin merino needs no extra room, and all 25 Adam & Westcott vests carry M through 2XL if you do want to go up.

What size vest do I need if I wear a large sweater?
Order L for a thin knit and XL for a thick one. Every one of the 25 vests in the range carries both sizes, so the choice is open on the whole collection.

Can I size up a vest if I wear 2XL?
On 21 of the 25 vests, yes. Four stop at 2XL, so check the size run first. The Packable Down Vest reaches 6XL.

Do Adam & Westcott vests come in XS?
10 of the 25 vests carry XS and one carries XXS, the Duck Down Vest at $59.98. The other 15 start at S or M.

How many sizes does a typical Adam & Westcott vest come in?
Seven. Runs span 5 sizes at the shortest to 10 at the longest, with the Packable Down Vest covering XS to 6XL.

Related reading: if you are still choosing between fills, the puffer vest versus fleece vest comparison covers warmth against weight, and the utility vest guide covers pocket layouts. For sizing across the rest of the range, see the Adam & Westcott size chart.