Calculating Inductance Value in AC RL Circuit Given Vs, Vr, I, and VL with Formulas

How do i calculate the value of an inductor in an AC RL circuit? 

What i know: 
Vs 
Vr 
I 
V(L) 

I think i am right in saying that source voltage and current has a phase angle of 0, and VL has a phase angle of 90. 

Please include step by step and all formulas. 
(make up values) 

Hello Paul.

Yes, VI [inductor current] will lag from VL [inductor voltage] by 90 degrees.
Are you calculating it in theory or do you have an actual inductor that you need to find the value of?

In theory, the inductance can be derived by having a sample sinusoidal source voltage of constant frequency and some predefined circuit values [we'll be dealing with phasors] and deriving the unknown inductance [by arriving first at the inductive impedance]. Voltage and current on at least one branch must be given in order to solve this.

In practice, I think the best way is to rely on a meter because there is a risk of saturating the inductor with a test circuit.

Thats all I can do.

Kudos,
Justin