everytime i try to import a static mesh from blender to UE the units are completely off. ive follow all the tutorials on youtube and from https://wiki.unrealengine/Static_Mesh_from_Blender#Unit_Scale_in_Blender exactly and it doesnt turn out the same for me. it says to go to scene, change units to metric and set scale to .01. i do that and export it to the engine and it becomes 1km when i place it. but in blender if i change the scale of my object to 400m and then export it to the engine then it scales down to 1m. what am i doing wrong?
Which blender version do you use + could you post your export settings. 
This is actually much easier than it was in UDK. When creating content in blender, just leave the scale at the default settings, and use blender units. When exporting to .fbx, leave the scale at 100%. One blender unit equals one centimeter in UE4; if you’re working in metric units (which you should be – it is much easier) there is no conversion needed.
I’ve found that unchecking “Convert Scene” in the UE4 import settings has made things more predictable for me.
We had alot of problems with this, finally a combination of several factors worked out. Set your default scene to metric with scale of .01… So when you load your scene it is already set properly… ALSO when you export set your fbx export to .01 ← this turned out to be the correct scale for export… Everyone kept saying that it had to be 100 or 1… This was not the case. Now we have absolutely no problems… Just make sure your dimensions are the actual size you want them in the N tab and export… Due to the radical scale issues we have had I hope this works for you. But like I said it works perfect for us.
did you remember to apply the scale to your object before exporting?