Begin With a Measured Foot, Not a Remembered Label
A familiar shoe size is only a useful starting point. Feet can differ from each other and can change with age, weight, pregnancy, injury, activity, or time of day. Brannock fitting guidance recommends measuring both feet and fitting the larger one, while Adidas advises measuring at the end of the day. Record a current measurement before comparing labels when fit or return cost matters.
Stand on a hard surface with normal weight on the foot. Mark the heel and the longest toe with the marking tool held upright, then measure between the marks. Repeat the process. An angled pencil, seated foot, thick outline, or measurement taken from a loose tracing can create enough error to select another row.
Keep Foot Length, Box Labels, and Shoe Interior Length Separate
Heel-to-toe foot length describes the body measurement used for the lookup. A CM or JP value printed on packaging can be a manufacturer label rather than the same physical foot length. Nike explicitly warns that the CM size shown on boxes and labels differs from Foot Length (cm). Shoe interior length is different again because a last includes design allowance and shape.
Write the quantity beside the number: measured foot length, printed CM label, or internal shoe measurement. This calculator accepts measured heel-to-toe length in centimetres or inches and Mondopoint millimetres. It does not reinterpret an unlabeled package number.
Understand Why Conversion Is a Table Lookup
ISO 19407:2023 provides technical and recommended conversion tables based on foot length, but describes them as guidance because sizing systems developed and were interpreted differently over time. That history is why a simple equation cannot turn every US label into one guaranteed UK or EU size.
A defensible converter names its chart, finds a discrete listed row, and reports whether the input was exact or between rows. It should not display an interpolated EU 42.7 when the selected chart lists 42 2/3 or 42.5. The nearby-row table makes the real grading steps visible.
Compare Manufacturer Charts Without Combining Them
For US men's 9, the Adidas adult chart lists US women's 10, UK 8.5, EU 42 2/3, and 26.3 cm heel-to-toe. Nike lists US women's 10.5, UK 8, EU 42.5, and a separate foot-length reference for its US men's 9 row. Both are internally valid chart lookups; neither proves the label for a third brand.
Choose one chart for the primary result. An alternate-chart illustration can expose variation, but do not take the US label from one row, the EU label from another brand, and the length from a third source. For a purchase, the exact product page outranks a general reference chart.
Handle Values Between Listed Rows Deliberately
A measured length may sit between two rows. Nearest-row handling minimizes numerical distance, while next-listed handling deliberately chooses the higher row. Nike advises sizing up when the measurement is between sizes. Adidas provides different guidance for a tighter or looser fit. Those directions are manufacturer context, not a universal medical or fitting rule.
Record which handling rule was used. If one foot falls on a row and the other falls between rows, use the larger relevant measurement as the comparison baseline, then consider the intended socks, activity, and product fit notes before deciding.
Treat Men's, Women's, and Unisex Labels as Chart Terms
A fixed men's-to-women's offset works only when the selected chart actually publishes that relationship. Adidas shows a one-size difference across the adult rows shared by its men's and women's columns; Nike shows 1.5. Those differences are useful for navigating departments, but they do not describe a person's foot width or identify a universal unisex conversion.
For unisex models, use the product's stated primary scale and conversion row. Compare the measured length, then review width or fit notes. Avoid changing departments by number alone when the model, last, or width offering also changes.
Add Width, Arch Length, and Trial Fit to the Decision
Brannock fitting uses heel-to-toe length, heel-to-ball or arch length, and width. It recommends comparing the two length readings and generally using the larger size indication. Width terms such as narrow, regular, wide, and extra wide are not standardized across manufacturers, so a length conversion cannot calculate them reliably.
A shoe can be the right nominal length and still fail at the toe box, instep, heel, or flex point. Orthotics, thick socks, foot swelling, and activity-specific motion add more context. Walk in the fully laced shoe when possible and use a practical return policy for online orders.
Build a Reproducible Online Shoe-Size Check
Keep the original measurement, units, selected chart, input system, between-row rule, matched row, and date checked. Revisit the manufacturer page because published charts and product guidance can change. A screenshot of only the final EU or US number removes the evidence needed to reproduce the lookup.
Use separate children's guidance for growing feet. For adult safety footwear, custom footwear, orthoses, persistent pain, numbness, deformity, or medical concerns, seek appropriate professional fitting or clinical advice. A browser chart can organize labels; it cannot inspect a foot or certify fit.
- Measure both feet while standing.
- Name the measurement and unit.
- Choose one published chart.
- Record exact or between-row status.
- Check width and product-specific fit separately.
- Confirm the current chart and return terms before purchase.
Frequently asked questions
What is a US men's size 9 in EU shoes?
In the Adidas adult reference, US men's 9 aligns with EU 42 2/3. In the Nike adult reference, US men's 9 aligns with EU 42.5. Check the exact product chart because EU labels are not universal across brands.
What is a US women's size 10 in men's shoes?
The Adidas adult chart aligns US women's 10 with US men's 9. The Nike adult chart aligns US women's 10 with US men's 8.5. Use the selected manufacturer chart and measured length rather than applying one fixed difference everywhere.
How do I convert foot length in cm to shoe size?
Measure both feet while standing, enter the longer heel-to-toe length, choose Foot length (cm), and select a reference chart. The result identifies an exact, nearest, or next listed row instead of inventing a fractional label.
Should I size up when my foot length is between sizes?
Nike recommends sizing up when a measured foot length falls between its listed sizes, while Adidas presents tight- and loose-fit directions. This calculator lets you compare nearest and next-listed rows, but the exact model's fit notes and return policy should decide the purchase.
Are Adidas and Nike shoe sizes the same?
Not at every label or foot length. Their published charts can assign different UK, EU, women's, or length references to the same US men's number. That is why the calculator requires a named reference chart.
What does Mondopoint shoe size mean?
Mondopoint is an ISO footwear sizing and marking system based on defined foot measurements and expressed in millimetres. A 263 mm input represents 26.3 cm of foot length context, but width and shoe shape still need separate checking.
References
These sources support the method or guidance used for Shoe Size Conversion Calculator. Verify time-sensitive rules at the source.
Try the calculator
Open Shoe Size Conversion Calculator, enter your scenario, and compare its supporting rows with this guide's method and checks.