Shoe Size Converter – US, EU, UK, CM

Shoe Size Systems Worldwide

There is no universal shoe sizing standard, and the lack of global harmonization has created a confusing landscape of incompatible systems. Knowing the differences helps you shop confidently for footwear from any country.

The main sizing systems are:

• US/Canada: Separate scales for men and women. Women's sizes run about 1.5 sizes larger numerically than the equivalent men's size. A women's US 9 equals a men's US 7.5.
• UK (British): Similar to US but typically 0.5–1 size smaller. A US men's 10 equals a UK 9.5. UK sizing is the same for men and women at the same foot length.
• EU (Paris points): Based on the French inch (pouce). Roughly calculated as: EU size = (foot length in cm × 1.5) + 2. The EU system is unisex — a EU 42 is the same foot length regardless of gender.
• Japan/CM: The most logical system — sizes are simply the foot length in centimeters. A Japanese size 27 means a 27 cm foot. No gender differentiation needed.
• Korea (mm): Similar to Japan but in millimeters. Korean size 270 = 27.0 cm = 270 mm foot length.
• Mondopoint: An ISO standard that specifies both foot length and width in millimeters. Used in some professional and military contexts for precision fitting.

Always measure your actual foot length rather than assuming your size transfers between brands or systems. A US size 10 in Nike running shoes may fit differently than a US size 10 in dress shoes from a different manufacturer due to variations in shoe lasts (the foot-shaped form used to construct shoes).

International Shoe Size Conversion Chart

Quick reference for converting shoe sizes across the major systems. All values are approximate — always try on shoes when possible or check the brand's specific size guide:

These conversions represent general industry approximations. Specific brands may deviate by half a size in either direction. For running shoes especially, many runners go up half a size to allow room for foot swelling during long runs and to prevent toenail bruising.

How to Measure Your Foot Correctly

Accurate foot measurement is the foundation of good shoe fitting. Shoe sizes are numerical abstractions — your actual foot dimensions are what matter. Here is how to measure correctly:

1. Time of day matters: Feet swell throughout the day, especially after standing or walking. Measure in the afternoon or evening when your feet are at their largest.
2. Trace both feet: Most people have one foot slightly larger than the other — sometimes by as much as half a shoe size. Always fit to the larger foot.
3. Stand while measuring: Foot length increases when you bear weight. Measure standing, not sitting, with your full weight on the foot.
4. Measure length and width: Place your foot flat on paper and trace the outline. Measure the longest distance (heel to longest toe) and the widest point.
5. Account for sock thickness: Wear the type of socks you plan to use with the shoes when measuring, especially for athletic or winter footwear.

Converting measurements to sizes: EU size ≈ (foot length in cm × 1.5) + 2. For example, 26 cm foot: EU ≈ (26 × 1.5) + 2 = 41. US men's: EU − 31.5 ≈ 9.5. This formula gives a good starting point; always verify with the brand's size chart.

Shoe Width Systems Explained

Width is often more important than length for shoe comfort, yet most online shopping focuses only on length-based sizing. Wearing the wrong width is the leading cause of foot pain from new shoes.

Width measurements vary by shoe size — a "wide" (E) in size 8 is narrower in absolute terms than a "wide" in size 12. If you consistently experience blisters on the sides of your feet, bunions, or toenail discomfort, you may need a wider width rather than a longer length. Common advice: if your foot overflows the insole edges when you stand, go wider.

Running Shoe Sizing: Special Considerations

Running shoe sizing follows different conventions from casual footwear. Most experienced runners and shoe fitting specialists recommend going up half to a full size from your street shoe size for running shoes. The reasons:

• Foot swelling: During runs exceeding 30–45 minutes, feet swell due to increased blood flow and heat. A snug fit at rest becomes painfully tight after 10 km.
• Toe box clearance: A thumb's width of space between your longest toe and the end of the shoe prevents toenail bruising and loss — a common problem for runners who size down.
• Toe movement: Running requires your toes to splay as your foot strikes the ground. A proper running shoe allows natural toe spread, which improves stability and reduces injury risk.
• Heel lock: Even in a properly sized running shoe, the heel should fit snugly with minimal slippage. If the heel slips but the toe box fits, try a different last shape rather than sizing down.

For running shoes specifically, always try them on in the afternoon (when feet are largest), wear your running socks, and walk/jog in the store before buying. The feel at rest is not representative of the feel at mile 5.

Children's Shoe Sizes

Children's shoe sizing follows different scales from adult sizing and varies by region. In the US, children's sizes start at size 0 (newborn) and run to size 13, after which they transition to adult sizes starting at 1 (US size 1 = EU 32–33).

Children's feet grow an average of 1–1.5 cm per year under age 3, and 0.5–0.8 cm per year through adolescence. Shoes should be replaced every 3–6 months for toddlers and every 6–12 months for school-age children. Always leave 1–1.5 cm (one thumb width) of growing room between the longest toe and the shoe end.

Brand-Specific Sizing Variations

Even within the same regional sizing system, different brands use different "lasts" (the 3D foot-shaped molds around which shoes are constructed). This creates brand-to-brand size variation that requires attention when buying online:

Running shoe brands:

• Brooks: Generally true to size with a medium-width last
• New Balance: True to size; wide range of width options (2A, B, D, 2E, 4E)
• Nike: Historically runs slightly narrow and small; recommend going up half a size for wide feet
• ASICS: Generally true to size in standard width; offers 2E wide options in many models
• Hoka: True to size but wider toe box than most — good for those with wide forefeet
• Saucony: True to size; most models have a moderate width
• Adidas: European brand; sizing runs slightly large compared to US brands in some models

When buying running shoes online, read reviews specifically mentioning fit and sizing. The sizing comments ("runs large/small/narrow/wide") in user reviews are often more reliable than official size charts for predicting how a specific model will fit your foot.

Shopping for Shoes Online: Tips for Getting the Right Fit

Online shoe shopping eliminates the ability to try on shoes before buying, making size knowledge critical. Here are strategies experienced online shoe shoppers use to minimize returns and exchanges:

Measure first, always: Do not rely on your "usual size." Foot size changes with age (feet flatten and lengthen slightly), and different brands size differently. Measure your feet using the method described above (trace on paper, measure afternoon/evening) and record your measurements in cm or mm. Compare directly to the brand's size chart rather than converting through other systems.

Check multiple conversion sources: Size charts from different sources often disagree by half a size. When in doubt, round up. A slightly too-large shoe can be managed with insoles; a too-small shoe causes real foot damage.

Read size-specific reviews: Filter product reviews by people with a similar foot length to yours. Reviews mentioning "true to size," "runs large," or "runs narrow" from people with your measurements are the most reliable guide. Sites like Running Warehouse and Road Runner Sports aggregate runner feedback on fit.

Know the return policy: Before buying any shoes online, confirm the return policy for unworn shoes. Most reputable athletic retailers allow free returns or exchanges. Zappos, for example, offers free 365-day returns specifically to support the trial-and-return cycle that shoe fitting requires.

Try brand-specific virtual fitting tools: Several major brands now offer augmented reality (AR) or photo-based foot measurement apps. Nike's Nike Fit app, ASICS' ASICS Runkeeper sizing guide, and similar tools use your phone camera to estimate foot dimensions. These are not perfectly accurate but can help identify your approximate size range before ordering.

Shoe Size and Foot Health

Wearing incorrectly sized shoes is a leading cause of preventable foot problems. Understanding the relationship between shoe sizing and foot health can prevent common injuries and long-term issues:

Too small/narrow: Causes bunions, hammertoes, blisters, toenail bruising (runner's toe), metatarsalgia (ball-of-foot pain), and nerve compression (Morton's neuroma). Tight toe boxes prevent natural toe splay and alter gait mechanics, potentially leading to ankle, knee, and hip compensation injuries.

Too large: Causes heel slippage leading to Achilles bursitis and blisters, toe-banging on downhills causing subungual hematoma (blood pooling under toenail), and instability that increases ankle sprain risk. Shoes that are too large force the foot to grip and pronate excessively to keep the shoe on.

Correct fit indicators: Standing in the shoe, you should have approximately 1 cm between your longest toe and the shoe end. The heel should feel snug with minimal slippage. The widest part of your foot should align with the widest part of the shoe without being compressed. The arch support (if any) should sit directly under your arch, not rolling in or out.

The American Podiatric Medical Association (APMA) recommends having feet professionally measured every few years, as foot size and shape change with age, pregnancy, and weight changes. Many adults wear shoes that are 1–1.5 sizes too small simply because they were measured as teenagers and never updated their size.