Calculating the saturation current of an inductor?
Best is to use manufacturers data.
Test in an oscillator. (See below)
Apply variable DC + AC  and monitor effect on AC as DC increased.




Oscillator method -  2. Above. 

Given:


A flyback converter/oscillator (eg a typical smps boost converter) operating in 'discontinuous mode' 
An oscilloscope
Variable load.


Iin is a triangle wave plus an off period.
As you increase the load towards saturation the straight portion of the triangle wave will start to assume an upwards kink - ie the rate of rise of current with time will increase as you enter saturation. 

Inductance will drop as the core enters saturation. More current further reduces inductance. 



From Left and middle and right