You can measure in Meshlab! There is a tool in the quick acces toolbar.
See below, please excuse my english and my french image !! :)
Measure in meshlab...
You can also reduce the number of element of your stl to import it in SW
Go to filters, Quadric Edge collapse decimation
SW can handle a maximum of 100 000 triangles for a surface importation and a maximum of 20 000 for a volume importation (you'll understand next)
Enter the number of triangles. 100 000 is for the best quality, like I said, if you want to open it in SW, but it's really long to open... . Anyway!
I usually lower the number by 5 to be sure I won't have one extra triangle.
As you can see, you are not exact (really close)!
Now you got to export your mesh
Open your Solidworks, select STL format and clic OPTION
Choose the lowest case for surface importation (that's what I talked about in step 3)
Now wait until your model is created...For the exemple I dropes triangles to 20 000.. That's too long for me with 100 000..
And you can now measure with measuring tool
There is an other way to deal with stl in SW, but I don't know everyone have the extension in SW..
You cannot measure quickly in this method, but you'll able to redraw a stl..
Export your mesh as .PLY file (.OBJ works fine too). No need to decrease the number of triangle.
Go to SW, open a new file and activate SCAN TO 3D extension
Right click on the toolbar and select Scan to 3D
Now open your file .PLY or .OBJ
(Sincerely, I don't know why solidworks isn't able to open STL file as a mesh file... You really need to change the format to tell him : ah Ok it's mesh and not a graphic image)
Now you see your mesh