Requirements: Max 2016 + Extension1/2 + SP3, Max 2017, Max 2018.
This MCG creates a bounding shape around your Spline. It was originally designed for splines...but you may use it for Mesh as well. This has the advantage over BBox as BBox cannot conform to the contours of your objects.
Installation: Scripting>Install Max Creation Graph...
Then can be found in Create>Shapes>Vu
Use it to obtain a 'footprint' of the object...or feed that footprint to Utility>Measure and get the length of the Bounding Shape.
ver 1.01: Now you can press F11 and you can get the Length.