How do I find my jacket size?

Measure your chest at its fullest point, just under the armpits, with a tape measure. In the US and UK, this measurement in inches is your jacket chest size. A 40-inch chest gives a jacket size of 40. Add a length suffix based on your height: Short (S) for heights under 5 foot 8 inches, Regular (R) for 5 foot 8 inches to 6 foot 1 inch, and Long (L) for above 6 foot 1 inch. EU sizes add approximately 10 to the US chest size: US 40 equals approximately EU 50.

What is the difference between US and European jacket sizing?

US and UK jacket sizes use chest circumference in inches as the primary number (such as 38, 40, 42). European jacket sizes use centimetres and are approximately equal to the US size multiplied by 2.54, then rounded: a US 40 chest equals about 102 cm, which corresponds to EU size 52 in most sizing systems. Italian suit sizes use a different scale again: a US 40 jacket is typically Italian size 50.

What does 40R mean in a jacket size?

40R is a jacket size where 40 refers to the chest circumference in inches and R means Regular length. This jacket is designed for someone with a 40-inch chest and a height between approximately 5 foot 8 inches and 6 foot 1 inch. The same chest measurement in Short length (40S) would suit someone under 5 foot 8 inches, and Long (40L) would suit someone above 6 foot 1 inch.

How do I convert my jacket size from US to European?

To convert a US jacket size to European, multiply the US chest size in inches by 2 and add 10. For example, a US 40 jacket chest equals 40 times 2 plus 10, which equals 90 plus 10, equals 100... actually the more accurate conversion is: EU size equals (US chest in inches times 2.54) rounded to the nearest even number divided by 2, then approximately. A simpler practical rule: US 38 is EU 48, US 40 is EU 50, US 42 is EU 52, US 44 is EU 54.

What is an athletic fit jacket?

An athletic fit jacket (also called a muscle fit) is cut with more room in the chest and shoulders compared with a regular fit, and with a more aggressively tapered waist. It is designed for individuals with a V-shaped torso: broad shoulders and chest relative to waist. Athletic fit suits are typically 3 to 5 inches narrower at the waist than the chest, compared with 2 to 3 inches for a slim fit and 1 to 2 inches for a classic or regular fit.

How much room should a jacket have?

A well-fitting jacket should have approximately 2 to 3 inches of ease (extra room) at the chest beyond your actual chest measurement in a classic regular fit. You should be able to slip a fist under the buttoned front without the button straining. The shoulders should end exactly where your natural shoulder ends, the sleeve should show about half an inch of shirt cuff below the jacket sleeve hem, and the jacket length should cover the seat when standing.

What jacket size is a 42 inch chest?

A 42-inch chest corresponds to a US and UK jacket size of 42. In EU sizing, this is approximately size 52. In Italian sizing, it is approximately size 52 as well (Italian and EU sizes differ slightly by brand but are close). The length suffix depends on height: 42S for under 5 foot 8 inches, 42R for 5 foot 8 to 6 foot 1, and 42L for above 6 foot 1.

Should I size up or down if I am between jacket sizes?

If you are between jacket sizes, size up and have a tailor take in the sides if needed. It is much easier and less expensive to have a jacket taken in at the sides than to let out a seam, which may not have adequate seam allowance. Sizing down causes pulling across the chest and shoulders, which cannot be corrected without major structural alterations. The shoulders of a jacket are particularly important: if the shoulders do not fit, no tailor adjustment can fix the garment economically.

What is the easiest measurement to use for jacket sizing?

The chest circumference is the primary measurement for jacket sizing. Measure around the fullest part of your chest under the armpits, with arms relaxed, over a light shirt. This single measurement determines the jacket chest size number in US, UK, and EU sizing systems. Shoulder width and body length add refinement but the chest measurement is the starting point for any jacket size recommendation.

How do jacket sizes differ for women?

Women's jacket sizes in the US use even numbers (2, 4, 6, 8, 10, 12, 14, etc.) that correspond to a standardised combination of bust, waist, and hip measurements rather than a simple chest measurement. The same jacket size number does not correspond to the same chest size across men's and women's systems. European women's jacket sizes use different numbers again (34, 36, 38, 40, 42, 44) based on a similar standardised measurement protocol.

Jacket Size Calculator – US, UK and EU Jacket Sizes

Jacket Size Calculator

The Jacket Size Calculator converts your chest, shoulder width, and body length measurements into jacket and suit sizes across US, UK, European, and Italian sizing systems. It accounts for fit type (regular, slim, or athletic) and returns the recommended size in each format. Use it to buy suits, blazers, and sport coats online without a tailor and to convert between sizing systems when shopping internationally.

US/CA	UK	EU/IT	FR	JP
M	M	48-50	48	L

US/CA

EU/IT

48-50

Size	Chest (in)	Chest (cm)
XS	32–34"	81–86 cm
S	35–37"	89–94 cm
MYou	38–40"	97–102 cm
L	41–43"	104–109 cm
XL	44–46"	112–117 cm
XXL	47–49"	119–124 cm
3XL	50–52"	127–132 cm

Size

Chest (in)

Chest (cm)

32–34"

81–86 cm

35–37"

89–94 cm

MYou

38–40"

97–102 cm

41–43"

104–109 cm

44–46"

112–117 cm

XXL

47–49"

119–124 cm

3XL

50–52"

127–132 cm

What Is the Jacket Size Calculator?

The Jacket Size Calculator converts your chest circumference, shoulder width, and height into jacket and suit sizes across the US, UK, European, and Italian sizing systems. Shoppers, stylists, and wardrobe managers use it to work out the correct size before buying online or from international retailers where sizing conventions differ. Jacket sizing uses a different convention in every major market: the US and UK express the chest size in inches; the EU uses centimetres; Italy uses a slightly different scale; and each system has its own length notation. According to guidelines referenced in the ASTM D6829 body measurement standard for men's apparel, chest circumference measured at the fullest point is the primary dimension for determining outerwear and jacket size across all systems.

Unlike shirt sizing, jacket sizing must account for three dimensions simultaneously: chest width, shoulder width, and body length. A jacket that fits the chest but has shoulders that overhang by an inch looks ill-fitting and cannot be corrected without major structural work by a master tailor. Conversely, jacket chest and waist room can be adjusted relatively easily. Given this, the shoulder measurement is the highest-priority fit dimension, and the calculator uses it alongside chest circumference to identify cases where a standard size may require a different-width shoulder than the chest size implies, such as for broad-shouldered or narrow-shouldered individuals.

How Jacket Sizing Systems Work

In the US and UK, a jacket size consists of a number and a letter: the number is the chest circumference in inches and the letter indicates the body length. Short (S) is designed for heights under 5 foot 8 inches, Regular (R) for 5 foot 8 inches to 6 foot 1 inch, and Long (L) for over 6 foot 1 inch. The chest number in a standard men's jacket corresponds approximately to the actual chest measurement plus 2 to 4 inches of ease. A man with a measured chest of 40 inches wears a size 40 jacket. The NIST body measurement guidelines for apparel confirm this relationship as the standard used across the US garment industry.

European jacket sizes are derived from the chest circumference in centimetres, divided by 2 and added to a constant offset, which produces numbers in the range of 44 to 60 for most adult men. The practical conversion rule is: EU size equals US size plus 10 (so US 38 equals approximately EU 48, and US 44 equals approximately EU 54). Italian sizing follows a similar but slightly different formula and is roughly equivalent to EU sizing for most brands. That said, fit philosophy varies significantly: Italian suits are cut with more structure and suppressed waist; British suits have a more padded shoulder; American suits have a fuller, boxier silhouette. As a result, the same numeric size across these systems may have different actual garment dimensions.

Jacket Size Conversion Chart

The table below shows common jacket size conversions across the four main systems. Length codes are omitted from this reference; add S, R, or L to the US/UK size based on your height.

US / UK Size	Chest (inches)	EU Size (approx.)	Italian Size (approx.)
36	36 in (91 cm)	46	46
38	38 in (97 cm)	48	48
40	40 in (102 cm)	50	50
42	42 in (107 cm)	52	52
44	44 in (112 cm)	54	54
46	46 in (117 cm)	56	56
48	48 in (122 cm)	58	58

Fit Types and When to Choose Each

Modern jacket sizing divides garments into fit categories that reflect different body shapes and style preferences. Classic or regular fit has the most room throughout: chest, waist, and back are cut generously with minimal suppression. Slim fit reduces the waist suppression to create a more tailored silhouette without changing the shoulder or chest width significantly. Athletic fit (also called muscle fit) maintains a wider chest and shoulder width while aggressively tapering through the waist, designed for the V-shaped torso that results from regular upper-body training. Choosing the wrong fit type and compensating by sizing up or down is a common cause of ill-fitting jackets: a slim-fit jacket in a larger size will have too much chest room rather than the correct athletic proportions.

In practice, body proportions that fall between fit categories may require alterations regardless of which size is chosen off the rack. A tailor can adjust chest and waist room, shorten sleeves, and take in or let out side seams, but cannot change shoulder width without rebuilding the garment from the shoulder seam outward. As a result, shoulder fit should be confirmed first by trying the jacket on or requesting a shoulder measurement from the manufacturer before ordering online. Given this, the calculator flags cases where the user's shoulder width measurement is disproportionate to their chest size, indicating that a standard-cut jacket in the calculated chest size may not fit at the shoulder.

Accuracy and Limitations

The jacket size calculator is accurate for the measurements entered using the conversion formulas above. Its practical accuracy depends on how carefully the chest measurement is taken: measuring too tightly over a compressed chest will produce a smaller size than necessary; measuring loosely will result in a jacket that is too large. Take the chest measurement over a light-weight shirt or T-shirt, with arms relaxed and the tape snug but not compressing the chest. Repeat three times and use the largest reading, as garment size should accommodate your largest chest position during normal movement.

The tool uses general size equivalences that represent typical conversion ratios. Actual garment dimensions vary significantly by brand even within the same nominal size: a size 40R from one manufacturer may have a chest of 42 inches in the garment, while another may have 44 inches for the same size label. Always consult the specific manufacturer's size chart and garment measurements before purchasing, particularly for jackets made in EU or Italian sizing for international brands where the fit philosophy differs from US or UK standards.

The Most Common Jacket Sizing Mistake

The error I see most often is choosing a jacket size based on chest measurement alone without checking the shoulder seam position on arrival. Many online purchases are returned not because the chest is wrong, but because the shoulder overhang by half an inch makes the jacket look sloppy. With that in mind, always ask the retailer for the garment's shoulder measurement (the distance across the back from shoulder seam to shoulder seam) before buying, and compare it to your own shoulder width measurement. This step is skipped most often when buyers assume that the shoulder fit follows automatically from the chest size, which it does for average body proportions but not for individuals who are notably broad or narrow-shouldered relative to their chest circumference.

Jacket Size Calculator