Globally there are 7 major shoe size systems, with the US, British, European and Japanese size system being the most common ones across the world.
The size conversion useful for people who shop on US or European online stores for shoes and clothings, which are usually cheaper than in your country.
The European shoe size system is less standardizes as others around the world. A French or a German shoe size can be totally different based on manufacture or brand. With that said, please use the chart as a guiding principle while knowing that sizes can and do vary by brand manufacturer and country.
International shoes size conversions: