If you export an FBX model, in this case from Blender, into Unity it might be really really really really tiny, even though you set it’s size up appropriately in Blender before exporting.
This is caused by the FBX importer in Unity, which for some reason imports at a scale of 0.01. Why? I’m not sure anyone knows, but if you encounter this problem be sure to check this first.
Click your imported model in the project panel.
In the Inspector, scroll down to the (FBXImporter) section.
Locate Scale Factor and change it to 1.
Now your model should appear… normal sized. Remember by default 1 == 1 meter.