[inglor_cz]

Is even a 13 kg dog "small"? It certainly does not feel small if you are carrying it upstairs.

[Scarblac]

It's American small.

[mattmaroon]

While there’s no formal definition, I think it isn’t. It would be considered medium sized. I live with a 4 lb dog.

I’d say 25-50 lbs would be medium, small below that and large above.