Size Guide
Size Guide
Our shirts run true to size for most men. The notes below should answer the question "what size do I order?" before you have to email us. If they don't, email us anyway — we read every message and reply within a business day.
Quick reference
Our model is 6'0", 185 lbs, with a 40-inch chest. He wears:
- The Bruce — Large
- The George — Large
- The Cassius — Large
If your dimensions are similar, Large is your answer.
How to measure yourself
You only need two measurements to size a Sir W. shirt: chest and height. A soft tape measure costs a dollar at any hardware store. Five minutes of effort saves you the cost of a return.
Chest
Wrap the tape around the fullest part of your chest, just under the armpits, with your arms relaxed at your sides. The tape should sit flat against your body — snug but not tight. Note the number in inches.
Height
You probably already know this one. Stand against a wall, mark the top of your head, measure to the floor.
How to read the tables
Our tables show body measurements — the actual circumference of your chest, in inches. Find the row where your chest measurement fits within the range. That's your size.
If you're between two sizes, see the Between sizes section below for guidance.
The Bruce — The Travel Button-Up
A slim-regular fit through the chest, with an untapered hem that sits cleanly whether you wear it tucked or untucked. True to size — most customers find their usual size works.
| Size | Chest (in / cm) | Length (in / cm) | Sleeve from Shoulder (in / cm) | Shoulder (in / cm) |
|---|---|---|---|---|
| S | 37.5" / 95 cm | 25" / 64 cm | 8 1/4" / 21 cm | 16 1/2" / 42 cm |
| M | 40.5" / 103 cm | 26" / 66 cm | 8 5/8" / 22 cm | 17 1/2" / 44 cm |
| L | 43.5" / 110 cm | 27" / 69 cm | 9" / 23 cm | 18 1/2" / 47 cm |
| XL | 46.5" / 118 cm | 28" / 71 cm | 9 3/8" / 24 cm | 19 1/2" / 50 cm |
| XXL | 48.5" / 123 cm | 29" / 74 cm | 9 3/4" / 25 cm | 20 1/2" / 52 cm |
Seven mother-of-pearl buttons up the front. Sleeve length measured from shoulder seam to cuff. Built to be worn tucked or untucked depending on the occasion.
The George — The All-Day Polo
Classic polo cut with a clean shoulder line and a hem that sits at the hip. Sized identically to The Bruce — if you wear M in the Bruce, you wear M in the George.
| Size | Chest (in / cm) | Length (in / cm) | Sleeve from Shoulder (in / cm) | Shoulder (in / cm) |
|---|---|---|---|---|
| S | 37.5" / 95 cm | 26" / 66 cm | 8 1/4" / 21 cm | 16 1/2" / 42 cm |
| M | 40.5" / 103 cm | 27" / 69 cm | 8 5/8" / 22 cm | 17 1/2" / 44 cm |
| L | 43.5" / 110 cm | 28" / 71 cm | 9" / 23 cm | 18 1/2" / 47 cm |
| XL | 46.5" / 118 cm | 29" / 74 cm | 9 3/8" / 24 cm | 19 1/2" / 50 cm |
| XXL | 48.5" / 123 cm | 30" / 76 cm | 9 3/4" / 25 cm | 20 1/2" / 52 cm |
Short-sleeve, two-button placket. Cut to drape cleanly whether you tuck it in for the office or leave it out for the weekend.
The Cassius — The Athletic Tee
A raglan-sleeve athletic cut. Trim through the shoulders, with a relaxed body that gives you room to move. Runs about one size larger in the chest than The Bruce and The George — if you wear M in the Bruce, you might prefer S in the Cassius if you want a slimmer fit.
| Size | Chest (in / cm) | Length (in / cm) | Bicep (in / cm) | Sleeve (in / cm) |
|---|---|---|---|---|
| S | 40.5" / 103 cm | 26 1/2" / 67 cm | 14 1/2" / 37 cm | 12 1/2" / 32 cm |
| M | 42.5" / 108 cm | 27 1/2" / 70 cm | 15 1/2" / 39 cm | 13" / 33 cm |
| L | 44.5" / 113 cm | 28 1/2" / 72 cm | 16 1/2" / 42 cm | 13 1/2" / 34 cm |
| XL | 46.5" / 118 cm | 29 1/2" / 75 cm | 17 1/2" / 44 cm | 14" / 36 cm |
| XXL | 48.5" / 123 cm | 30 1/2" / 77 cm | 18 1/2" / 47 cm | 14 1/2" / 37 cm |
Raglan sleeves give you full range of motion in the shoulder. Designed to work as a base layer, a tee on its own, or under a button-up.
Between sizes? Here's how to decide
If your chest measurement falls between two sizes, the answer usually depends on what you plan to do with the shirt.
Size down if you want:
- A trimmer, more tailored look
- The shirt to sit close to the body
- A slim modern cut that reads "fitted"
Size up if you want:
- A more relaxed, lived-in fit
- Room to layer underneath (long sleeve under the Cassius, for example)
- Movement for sport, hiking, or active wear
When in doubt, size to your chest measurement and the length will follow. Merino does have a slight stretch with wear, so a shirt that feels snug-but-not-tight on day one usually relaxes into a perfect fit by week two.
Care and longevity
Merino is durable but not invincible. Follow our Care Guide and a Sir W. shirt should last you five years or more of regular wear. Ignore it, and you could shrink it down a size in one wash. The choice is yours.
Still not sure?
Email us at gday@sirwmerino.com with your height, weight, chest measurement, and what you're hoping the shirt will do for you. We'll recommend a size, and if we get it wrong, we'll cover the exchange.
A real person reads every message and replies within one business day.
Featured collection
Spring Collection '26
