What size shoe is a 44?

The EU Size 44 corresponds to the US men’s Shoe Size 11 according to the ISO standard.

Is a size 10 shoe a 44?

The exact dimensions of a UK 10 (measured by foot length) as defined by ISO 19407 is 279.4mm, whereas an EU 44 is 280mm. As you can see, a UK 10 is only slightly smaller than an EU 44.