What Is CN 40 Shoe Size? Conversion & Fit

CN 40 generally corresponds to a foot measuring about 24.5–25.0 cm (9.6–9.8 inches). One gender-specific conversion chart places it at 24.5 cm, while other commercial charts place it at approximately 25 cm. (Compare the gender-specific CN 40 conversions)

As a quick conversion, CN 40 is commonly around US women’s 8.5–9, US men’s 7–7.5, UK 6–6.5, or EU 39–40. One chart supplies the upper end of those ranges—25 cm, US women’s 9, US men’s 7.5, UK 6.5, and EU 40. (See the 25 cm CN 40 conversion)

These figures are only a starting point. Other charts place the same two-digit label at US men’s 7 and US women’s 8.5, and at least one gives US men’s 6. The product-specific foot-length chart is therefore the best basis for choosing—not the number 40 by itself. (Review an old-system CN 40 conversion)

CN 40 conversion at a glance

The most useful practical range is:

Measurement or system	Approximate CN 40 equivalent
Foot length	24.5–25.0 cm / 9.6–9.8 in
US women’s	8.5–9
US men’s	7–7.5
UK	6–6.5
EU	39–40

Treat the table as a common conversion cluster, not a guaranteed fit or a complete record of every published conversion. The figures combine charts that use different gender categories and different interpretations of the CN label. They do not establish one universal Chinese size standard.

The outliers matter. One of the cited gender-specific charts converts CN 40 to US men’s 6, UK 5.5, EU 39, and 24.5 cm. Another international chart gives UK 6, EU 38.5, and 24.8 cm for China 40. (See the chart listing China 40 at 24.8 cm)

Another retailer guide maps CN 40 to EU 39.5 and UK 7. Together, the supplied charts place CN 40 at approximately EU 38.5, 39, 39.5, or 40, depending on the chart being used. (See the CN 40 to EU 39.5 retailer conversion)

This disagreement does not mean every conversion is equally suitable for a particular shoe. It means the label cannot be separated from its chart. Gender category, brand, shoe last, width, foot shape, construction, and the seller’s labeling convention can all change which international equivalent is most useful.

Why CN 40 is not automatically EU 40

No, a CN 40 label should not automatically be read as EU 40. The charts reviewed for this comparison map it to EU sizes from approximately 38.5 through 40.

The problem is that sellers do not always use “CN” in the same way. Across commercial and retailer charts, a two-digit CN number may represent:

• An older two-digit Chinese sizing convention.
• A commercial Euro-style conversion used on a marketplace or retailer chart.
• A retailer’s own chart for the products it sells.
• A number presented ambiguously or confused with an EU label.

Consequently, two shoes advertised as CN 40 do not necessarily correspond to the same foot length.

Some brand charts avoid this ambiguity by displaying Chinese sizing as a three-digit millimeter value. Nike China, for example, labels the relevant row “China size—MM.” On its men’s footwear chart, EU 40 corresponds to CN 250, together with US men’s 7, US women’s 8.5, and UK 6.

That is a bounded, brand-specific example. Nike’s chart does not contain a Chinese size labeled simply “40,” so it does not prove that every marketplace shoe marked CN 40 is equivalent to Nike’s EU 40 or CN 250. It only demonstrates why a clearly identified millimeter label can be easier to interpret than an unexplained two-digit number.

If a seller lists both CN and EU values, do not assume that identical-looking numbers mean identical sizes. Read across the exact product row and prioritize a stated foot-length measurement.

CN 40 versus CN 250

A three-digit CN 250 label generally means approximately 250 mm, or 25 cm, of foot length—when the chart identifies the number as a length-based Chinese size. By contrast, CN 40 is a two-digit label whose conversion depends more heavily on the seller’s or brand’s system.

Several commercial charts pair old-style CN 40 with CN 250 or a 25 cm foot. That association explains why shoppers often see the two labels treated as equivalents. It is still not safe to assume that they are interchangeable on every listing.

Use the information provided with the product:

What the listing says	How to interpret it	Best next step
CN 250	Start with a 250 mm foot-length interpretation	Confirm the chart labels it as foot length
CN 40 plus a cm range	Use the stated range as the primary reference	Match it to your longer foot
CN 40 plus CN 250	Treat 250 mm as the clearer reference	Check width and product fit notes
CN 40 only	The sizing system is uncertain	Consult the chart or ask the seller

The words attached to the measurement are important. Foot length, insole length, and internal shoe length are not interchangeable. A listing that states only “25 cm” has not provided enough information unless it explains what was measured.

Do not assume that a 250 mm insole is intended for a 250 mm foot. Instead, ask the seller whether the number describes the intended foot length, the removable insole, or the usable space inside the shoe.

How to check whether CN 40 will fit

Measure both feet while standing before using the seller’s chart. A simple wall method keeps the measuring points clear:

1. Put a sheet of paper on a hard floor with one short edge touching a wall.
2. Stand on the paper with your heel lightly against the wall.
3. Keep your weight on the foot and mark the end of the longest toe.
4. Measure from the wall-facing edge of the paper to the toe mark.
5. Repeat with the other foot.
6. Use the longer measurement when reading the product chart.

Alternatively, trace each foot while standing, keeping the pencil upright, and measure from the back of the heel to the longest toe. Do not mix a seated measurement for one foot with a standing measurement for the other.

For example, if your longer foot measures 24.8 cm, look for a seller row that explicitly includes 24.8 cm, such as a stated 24.5–25.0 cm foot-length range. That is more useful than ordering solely because the product is labeled 40.

Next, check what kind of chart you are reading:

• Gender category: Women’s and men’s conversions can assign different US or UK numbers to the same CN label.
• Measurement type: Confirm that the centimeter or millimeter value means foot length rather than insole or internal length.
• Width and shape: A suitable length does not establish that the toe box, forefoot, or instep will fit.
• Construction: The shoe’s last and upper can affect how much usable room it provides.
• Socks: Compare the shoe with the type of socks you expect to wear.
• Fit notes: Follow clear, product-specific guidance rather than a universal instruction to size up.

Do not automatically order a larger size simply because the shoe comes from China. The supplied retailer recommendations are not consistent enough to support a universal size-up rule.

If the listing supplies no foot-length measurement, ask the seller whether “40” means CN 40, EU 40, or a product-specific code. Also ask which measurement method its chart uses and check the exchange or return policy before ordering.

CN 40 is best treated as a starting label. A foot around 24.5–25.0 cm commonly falls near this size, but measuring both feet and matching the longer one to the specific product’s stated foot-length range gives you a more dependable basis for choosing.