How can the success of the coaching process be measured?

Measurement may be thought of in two distinct ways: external indicators of performance and internal indicators of success. 

Ideally, both are incorporated.  

Examples of external measures include achievement of coaching goals established at the outset of the coaching relationship, increased income/revenue, obtaining a promotion, performance feedback that is obtained from a sample of the individual’s constituents (e.g., direct reports, colleagues, customers, boss, the manager him/herself), personal and/or business performance data (e.g., productivity, efficiency measures). The external measures selected should be things the individual is already measuring and has some ability to directly influence.  

Examples of internal measures include self-scoring/self-validating assessments that can be administered initially and at regular intervals in the coaching process, changes in the individual’s self-awareness and awareness of others, shifts in thinking that create more effective actions, and shifts in one’s emotional state that inspire confidence.