On each product page there is a size chart tab positioned under the 'Add to Basket' button, as shown on the image below highlighted in red. The size chart is individual to each product, if a size chart isn't shown it is because it is a one size fits all product. The size charts are carefully laid out to show the sizes in both cms and inches depending on your preference and also the size conversions eg EU, UK, USA which is more common for the womens sizing as shown below.
Once you click on the 'Size Guide' tab, you will see the sizes clearly shown, in both cms and inches.
For the Womens Sizes, the UK/USA/EU size conversions are clearly shown so you can choose your preference.