Shirt Size Converter
Convert shirt sizes between US, UK, EU, and Asian systems for men and women. Enter values for instant results with step-by-step formulas.
Calculator
Adjust values & calculateComplete Size Chart (Men)
| US | UK | EU | Asia | Chest |
|---|---|---|---|---|
| XS | XS | 44 | M | 34-36 in |
| S | S | 46 | L | 36-38 in |
| M | M | 48 | XL | 38-40 in |
| L | L | 50 | XXL | 40-42 in |
| XL | XL | 52 | XXXL | 42-44 in |
| XXL | XXL | 54 | 4XL | 44-46 in |
| 3XL | 3XL | 56 | 5XL | 46-48 in |
Formula
Shirt sizes are converted using standardized international sizing tables that map equivalent sizes across US, UK, EU, and Asian systems. Chest measurements in inches provide the underlying physical dimension that connects all systems. Asian sizes typically run 1-2 sizes smaller than Western equivalents.
Last reviewed: December 2025
Worked Examples
Example 1: Convert US Medium to International Sizes
Example 2: Convert EU 42 Women to US Size
Background & Theory
The Shirt Size Converter applies the following established principles and formulas. Unit conversion is the process of expressing a quantity in a different unit of measurement while preserving its physical meaning. At the foundation of modern measurement lies the International System of Units (SI), which defines seven base units: the meter for length, kilogram for mass, second for time, ampere for electric current, kelvin for thermodynamic temperature, mole for amount of substance, and candela for luminous intensity. All other units, called derived units, are defined as algebraic combinations of these seven. Dimensional analysis is the principal method for performing unit conversions. By treating units as algebraic quantities that can be multiplied, divided, and cancelled, a conversion factor chain allows a value expressed in one unit to be rewritten in another without altering its physical magnitude. For example, to convert 60 miles per hour to meters per second, one multiplies by a chain of conversion factors each equal to one: (1609.34 m / 1 mile) × (1 hour / 3600 s). Metric prefixes enable compact expression of quantities across extreme ranges of magnitude. Standard prefixes span from nano (10^-9) through micro (10^-6) and milli (10^-3) up through kilo (10^3), mega (10^6), and giga (10^9), and beyond in both directions. These prefixes are strictly multiplicative and apply consistently to any SI base or derived unit. Temperature conversions require affine transformations rather than simple scaling. To convert Celsius to Fahrenheit the formula is °F = (°C × 9/5) + 32, while the conversion to the absolute Kelvin scale is K = °C + 273.15. These formulas reflect the different zero points and degree-size conventions of each scale. Significant figures govern how precision is preserved through calculations. A result should not express more precision than the least precise input value permits. In digital storage, IEEE and IEC standards distinguish between decimal prefixes (kilobyte = 1000 bytes) and binary prefixes (kibibyte = 1024 bytes), a distinction that has practical consequences for how storage capacity is reported by manufacturers versus operating systems. Unit coherence — ensuring that all quantities in an equation share a consistent unit system — is essential for obtaining correct results.
History
The history behind the Shirt Size Converter traces back through the following developments. Human beings have been measuring and comparing quantities since before recorded history. The earliest known measurement units were body-based: the cubit (the distance from elbow to fingertip), the foot, the hand, and the digit. The furlong originated as the length of a furrow a team of oxen could plow without resting. These anthropomorphic standards were practical for local use but differed between regions and kingdoms, creating persistent difficulties in trade and construction. The ancient Egyptians standardized the royal cubit at approximately 52.4 centimeters and distributed calibrated granite rods to ensure consistency across building projects, including the pyramids. Roman engineers used the mile (mille passuum, one thousand double paces) and spread these standards throughout their empire via road networks. Despite these efforts, measurement diversity persisted across medieval Europe, hampering commerce. The French Revolution created political will for radical standardization. In 1795 France officially adopted the metric system, defining the meter as one ten-millionth of the distance from the equator to the North Pole along the Paris meridian. This gave the world its first fully decimal, rationally constructed measurement system. The Metre Convention of 1875 established the International Bureau of Weights and Measures (BIPM) in Sevres, France, creating a permanent international body to maintain physical artifact standards and coordinate global metrology. For over a century, the kilogram was defined by a platinum-iridium cylinder locked in a vault near Paris. In 1999, a stark demonstration of what unit inconsistency costs occurred when NASA's Mars Climate Orbiter was lost because one engineering team used pound-force seconds while another used newton seconds. The spacecraft entered the Martian atmosphere at the wrong angle and was destroyed, at a cost of 327 million dollars. In 2019 the SI underwent its most significant revision, redefining all seven base units in terms of fixed numerical values of fundamental physical constants such as the speed of light, Planck's constant, and the elementary charge. This eliminated any reliance on physical artifacts and made the measurement system permanently stable and universally reproducible.
Frequently Asked Questions
Formula
Size Conversion = Lookup Table(Gender, Input System, Input Size)
Shirt sizes are converted using standardized international sizing tables that map equivalent sizes across US, UK, EU, and Asian systems. Chest measurements in inches provide the underlying physical dimension that connects all systems. Asian sizes typically run 1-2 sizes smaller than Western equivalents.
Worked Examples
Example 1: Convert US Medium to International Sizes
Problem: A man wears a US Medium shirt. What are the equivalent sizes in UK, EU, and Asian systems?
Solution: US Medium = chest 38-40 inches (96-102 cm)\nUK equivalent: M (same letter system)\nEU equivalent: 48\nAsian equivalent: XL (Asian sizes run smaller)\nUS Numeric (dress shirt): 15.5-16 neck\nFor Asian shopping: order XL instead of M
Result: US: M | UK: M | EU: 48 | Asia: XL | Dress: 15.5-16
Example 2: Convert EU 42 Women to US Size
Problem: A woman sees a European size 42 blouse online. What US size should she order?
Solution: EU 42 = US XL\nUK equivalent: 14\nAsian equivalent: XXL\nUS Numeric: 16-18\nChest measurement: 39-41 inches (99-104 cm)\nFor Asian retailers: order XXXL or check measurements
Result: EU 42 = US XL | UK 14 | Asia XXL | Chest: 39-41 in
Frequently Asked Questions
How do US shirt sizes differ from European sizes?
US and European shirt sizes use completely different numbering systems that can cause confusion when shopping internationally. US sizes for men use letter designations (S, M, L, XL) or neck measurements in inches (15, 15.5, 16), while European sizes use even numbers starting around 44 and increasing in increments of 2 (44, 46, 48, 50, 52). A US Medium for men corresponds to approximately an EU 48, while a US Large is about an EU 50. For women, US sizes typically use even numbers (2, 4, 6, 8, 10) or letter sizes, while European sizes start around 34 and go up. The conversion is not always exact because brands interpret sizing differently. European sizes tend to run slimmer in cut, so even when the chest measurement matches, the overall fit may feel tighter through the body and sleeves.
Why are Asian shirt sizes different from Western sizes?
Asian shirt sizes run significantly smaller than Western sizes because they are designed for different average body proportions. The average Asian male has a smaller frame, narrower shoulders, and shorter torso compared to the average Western male. As a result, a size L in most Asian countries corresponds roughly to a US Small or Medium. This means Western consumers typically need to size up by 1 to 2 sizes when purchasing Asian-manufactured clothing. Japanese sizing tends to be the most consistent among Asian countries, while Chinese sizing can vary considerably between manufacturers. Korean sizing has recently shifted to be closer to European standards as brands target international markets. When shopping on Asian e-commerce platforms, always check the specific measurements in centimeters provided rather than relying on the letter size designation alone.
How do I measure my chest for accurate shirt sizing?
To measure your chest accurately for shirt sizing, you need a flexible measuring tape and ideally someone to help you. Stand straight with your arms relaxed at your sides. Wrap the measuring tape around the fullest part of your chest, typically across the nipple line and around the shoulder blades. The tape should be snug but not tight enough to compress the skin. For men, this measurement usually determines your shirt size directly. For women, measure both the bust (fullest point) and the underbust for more accurate sizing. Take the measurement while wearing a well-fitting non-padded bra for the most accurate result. Record the measurement in both inches and centimeters. If your measurement falls between two sizes, size up for a relaxed fit or down for a slim fit. Measure at the same time of day for consistency, as body measurements can fluctuate slightly.
Do UK and US shirt sizes match for men?
UK and US shirt sizes are very similar for men and use the same letter-based system (S, M, L, XL, XXL), with both based on chest measurements in inches. A US Medium and a UK Medium both typically correspond to a 38 to 40 inch chest. The primary difference lies in the cut and fit rather than the size designation itself. British shirts tend to have a slightly slimmer cut through the body compared to American shirts of the same labeled size. The collar size system is also shared, with both countries using inches (14.5, 15, 15.5, 16, etc.). However, sleeve lengths can differ because US dress shirts specify exact sleeve lengths while UK shirts often use standardized short, regular, and long sleeve categories. When converting between the two systems, the size label itself usually stays the same, but trying on the garment is recommended due to cut differences between brands.
How do I convert dress shirt sizes to casual shirt sizes?
Dress shirts and casual shirts use different sizing systems that can be confusing when cross-referencing. Dress shirts for men are typically sized by neck measurement in inches (14, 14.5, 15, 15.5, 16, 16.5, 17) combined with sleeve length, while casual shirts use letter sizes (S, M, L, XL). The general conversion is: neck 14 to 14.5 equals Small, 15 to 15.5 equals Medium, 16 to 16.5 equals Large, 17 to 17.5 equals XL, and 18 to 18.5 equals XXL. However, this conversion assumes a standard body proportion where neck size correlates with chest size. People with athletic builds (larger chest relative to neck) or heavier builds (larger neck relative to chest) may find that their dress shirt neck size does not match their best casual shirt size. In those cases, prioritize chest measurement for casual shirts and neck measurement for dress shirts.
Why do shirt sizes vary so much between brands?
Shirt sizes vary between brands due to several factors including target market demographics, vanity sizing practices, manufacturing tolerance, and design philosophy. Vanity sizing, where brands label garments with smaller numbers than actual measurements to flatter customers, has become widespread. A Medium from Brand A might have a 40-inch chest while Brand B Medium has a 42-inch chest. Fast fashion brands often have less consistent sizing due to manufacturing across multiple factories with varying quality controls. Premium brands generally maintain more consistent sizing but may target specific body types. European brands tend to run slimmer than American brands at the same size designation. Heritage brands that have existed for decades may have gradually increased their sizes over time through vanity sizing while keeping the same labels. The best strategy is to learn your measurements in inches and centimeters and check each brand specific size chart before purchasing.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy