Enter your neck measurement (and your sleeve length if you have it) and we will give you your dress shirt size: the numeric neck size, the sleeve band, the S to XXL letter size, and the EU collar number. Add your chest measurement and we will tell you which cut to buy.
A dress shirt is the one garment men still buy by actual body measurements, which should make it the easiest thing in the store. It would be, if the tag did not encode two measurements, a rounding convention, and a comfort allowance nobody explains. This page explains them. Measure your neck, and in one step you get the numeric size on the tag, the letter size on the casual rack, and the EU number on the imported shirt.
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How shirt sizing works
The size on a dress shirt tag is not your neck measurement; it is your neck measurement plus breathing room. The industry convention is to add about half an inch to the snug measurement, then round to the half inch, because collars come in half inch steps. Sleeves are simpler: whole inches, measured from the center back of your neck over the shoulder to the wrist bone, and often banded in pairs (34/35) on ready-to-wear shirts. The letter sizes on casual shirts map onto collar ranges, so one neck measurement really does size your whole shirt drawer.
The formula
collar size = neck + 1/2, rounded to the nearest 1/2 inch
sleeve size = sleeve length, rounded up to the whole inch
EU size = collar size × 2.54, rounded to the whole cm
Neck is your snug measurement at collar height in inches (we convert centimeters for you). The half inch added is the standard comfort allowance; the collar buttons over your neck, not onto it.
Worked example
Your neck measures 15.0 inches snug. Add the half inch allowance: 15.5, already on a half inch step, so your collar size is 15.5. That sits in the Medium band (15 to 15.5). EU size: 15.5 × 2.54 = 39.4, rounds to 39. Your sleeve measures 33.5 inches, which rounds up to 34, so on a banded shirt you want 34/35. You are a 15.5 x 34/35, a Medium, and an EU 39: three tags, one tape measure.
Collar size to letter and EU size
| Collar (in) | Letter size | EU collar | Fits chest (in) |
|---|
| 13 to 13.5 | XS | 33 to 34 | 33 to 34 |
| 14 to 14.5 | S | 36 to 37 | 35 to 37 |
| 15 to 15.5 | M | 38 to 39 | 38 to 40 |
| 16 to 16.5 | L | 41 to 42 | 41 to 43 |
| 17 to 17.5 | XL | 43 to 44 | 44 to 46 |
| 18 to 18.5 | XXL | 45 to 47 | 47 to 49 |
| 19 to 19.5 | 3XL | 48 to 50 | 50 to 52 |
The chest column is the body measurement each letter size is cut for in a classic fit. If your chest lands in a different row than your neck, do not split the difference: fit the collar and fix the body with the cut, as below.
Fit the collar, choose the cut
Here is the mistake that fills donation bins: buying a bigger neck size to get room in the chest, or a slim collar to avoid a tent. The collar is the one part of a shirt no tailor can meaningfully change and the one part that has to be exact, especially under a tie. So fit the collar first, always. Then look at where your chest falls: if it is a size band above your neck size, buy your collar size in a classic or relaxed cut, and if it is a band below, buy your collar size in a slim or tailored cut. The cut names vary by brand but the principle does not, and it is why the calculator asks for your chest as an optional third number.
Frequently asked questions
How do I measure my neck size for a dress shirt?
Wrap a soft measuring tape around your neck at the height where a collar sits, which is just under the Adam's apple, over the two tendons at the back. Keep the tape level and snug but not tight, and slide one finger under it before reading. Round nothing yet; give the calculator the raw number and it will add the comfort allowance for you.
What do dress shirt size numbers like 15.5 x 34/35 mean?
The first number is the collar size in inches, so a 15.5 fits a collar that measures 15.5 inches around when buttoned. The second is sleeve length in inches, measured from the center back of the neck, over the shoulder, down to the wrist. Many brands band two sleeve lengths together (34/35) and split the difference in the cuff placement.
How do I measure sleeve length?
You need a helper for this one. Stand with your arm relaxed and slightly bent. Start the tape at the center back of your neck (the bump at the base), run it across the top of your shoulder, down the outside of your arm past the elbow, and stop at the wrist bone. That full path, typically 32 to 37 inches, is your sleeve length. Measuring down a straight arm from the shoulder seam gives a number 2 to 3 inches short.
Should I size up if I am between shirt sizes?
For the collar, yes, always. A collar that is half an inch too small is unwearable by 2 pm, while one half an inch too big just looks slightly relaxed. Shirt collars also shrink slightly in the first few washes, which is another vote for the larger size. For sleeves, take the longer band too; cuffs can be worn a touch loose but cannot grow.
What letter size is a 15.5 inch neck?
In standard US menswear sizing, a 15 to 15.5 inch collar is a Medium. The usual mapping runs: 14 to 14.5 Small, 15 to 15.5 Medium, 16 to 16.5 Large, 17 to 17.5 XL, 18 to 18.5 XXL. Letter-sized casual shirts are cut to those collar equivalents, which is why a man who wears a 15.5 dress shirt usually wears a Medium polo.
How do EU shirt sizes work?
EU collar sizes are simply your collar measurement in centimeters, so EU 39 fits a 39 cm collar, which is a US 15.5. Multiply the US size by 2.54 and round: US 15 is EU 38, US 16 is EU 41, US 17 is EU 43. UK sizes use the same inches as the US, so a UK 15.5 and a US 15.5 are the same shirt.
What is the difference between slim fit and classic fit?
The collar and sleeve are the same for a given size; the difference is fabric through the chest and waist. A classic fit cuts roughly 4 to 6 inches of ease over your chest measurement, a slim fit closer to 2 to 4. That is why the right move is to fit the collar first, then pick the cut that matches your build: slim if your chest runs small for your neck size, classic or relaxed if it runs large.