About the Collar Size
This calculator converts neck circumference into a standard US/UK dress shirt collar size and its EU equivalent. It is meant for anyone shopping for a fitted dress shirt who has a neck measurement in centimeters but needs the size printed on shirt tags.
How It Works
Enter your neck circumference in centimeters, and the tool converts it to inches, then rounds that figure to the nearest half inch to produce the US/UK collar size, since dress shirts are typically sized in half-inch increments. The same centimeter value, rounded to a whole number, is shown as the EU collar size.
Formula & Methodology
The centimeter measurement is divided by 2.54 to convert it to inches. That inch value is then multiplied by 2, rounded to the nearest whole number, and divided by 2 again, which is the standard technique for rounding to the nearest half unit. The EU size skips the inch conversion entirely and just rounds the original centimeter measurement to a whole number, since European sizing labels use centimeter neck measurement directly as the size number.
Examples
A 40 cm neck measurement
Entering 40 cm converts to about 15.75 inches, which rounds to a US/UK collar size of 15.5 or 16.0 (rounding 15.75 to the nearest half gives 16.0), alongside an EU size of 40.
A 38 cm neck measurement
Entering 38 cm converts to about 14.96 inches, which rounds to a US/UK collar size of 15.0, alongside an EU size of 38.
Advantages
- Converts a metric neck measurement straight into the half-inch increments used on actual dress shirt size tags.
- Shows both US/UK and EU sizing at once, useful when comparing shirts from different regional brands.
- Removes the manual step of rounding an inch conversion to the nearest half size.
Common Mistakes
- Measuring the neck too tightly, which produces a collar size that feels constricting once the shirt is buttoned and a tie is added.
- Confusing collar size (a neck measurement) with overall shirt size (small, medium, large), which factors in chest and sleeve length too.
- Rounding the inch conversion down instead of to the nearest half size, resulting in a shirt that fits too snugly.
Edge Cases to Watch For
- The US/UK size always lands on a half-inch increment (such as 15.5 or 16.0), matching how dress shirts are actually manufactured and labeled.
- The EU size is a direct rounded centimeter figure and does not go through the inch conversion, so it can diverge slightly from simply converting the US/UK size back to centimeters.
- The calculator does not adjust for shirt fabric or brand-specific fit differences, which can shift the ideal size by half an inch in either direction.
Common Use Cases
- Online shoppers converting a tape-measure neck reading in centimeters into the shirt size needed to order the right fit.
- Travelers or expats comparing shirt sizing between US/UK and EU retailers before buying.
- Tailors or clothing retailers quickly cross-referencing a customer's metric measurement against standard collar size charts.