How to measure the impact of a mentoring program: four levels and a simple cost calculation

In budget discussions, mentoring programs usually face the same question: “What did this program deliver?” That question is hard to answer at the end of a cohort, and easy if you set up the right measurement at the start.

Measurement at four levels

You can adapt the four-level approach widely used in training evaluation to mentoring.

Level	Question	Example indicator	When
1. Participation and satisfaction	Did sessions happen, and did people find them useful?	Share of pairs meeting each month, session satisfaction	Every month
2. Learning	Did the mentee progress on their target area?	Goal progress, mentor assessment	Mid-cohort and end of cohort
3. Behavior	Do they act differently at work?	Change in 360 assessment	Start and end of cohort
4. Business results	Did the target number change?	Retention, promotion, role change, time to readiness	After 12 months

Level one is for running the program; level four is for defending it. Measure both.

Don’t forget the baseline

To show change, you need a starting point. Before the program begins:

• Measure mentees’ development areas with a 360 assessment or manager input.
• Record the last 12 months of the target business indicator.
• If possible, identify a similar group that isn’t taking part in the program.

Participants vs. non-participants

The clearest way to show mentoring’s effect on business results is to compare a participating and a non-participating group on the same indicator. For example, after 12 months:

Group	People	Still with the company after 12 months	Retention
New managers in the program	30	27	90%
New managers not in the program	40	31	78%

The figures in the table are illustrative.

Be careful when interpreting this comparison. People who volunteer for a program may already be more motivated. Keeping the groups similar in role, tenure and location makes the result more reliable. Academic research also shows that employees who receive mentoring report higher career satisfaction and more promotions; for example, the 2004 meta-analysis by Allen and colleagues summarizes these findings.

A simple cost calculation

Senior leadership usually wants to see the figure in money terms. A simple calculation for retention:

1. People leaving per year = group size × annual turnover rate
2. Cost of one departure = total annual cost per person × loss rate
3. Departures prevented = people leaving per year × expected reduction
4. Savings = departures prevented × cost of one departure

The loss rate covers hiring, onboarding, lost productivity and the cost of the vacant position. Set this rate using your own HR data and state it clearly in the report as an assumption. To try it with your own numbers, use the cost calculator.

Return on investment is calculated as follows:

Return on investment (%) = (savings − program cost) ÷ program cost × 100

In addition to software and service fees, include the time mentors and mentees spend in sessions in the program cost. A calculation that leaves out time costs you senior leadership’s trust.

Reporting to senior leadership

The end-of-cohort report should fit on one page and follow this order:

1. The program’s business goal (the one sentence you wrote at the start)
2. Participation: how many pairs, how many sessions, satisfaction
3. Development: goal progress and 360 change
4. Business results: participant vs. non-participant comparison
5. Cost and savings, with their assumptions
6. A recommendation for the next cohort

A report’s strength comes not from the size of its numbers but from the clarity of its assumptions. A report that states its assumptions openly earns more trust than an inflated one.

To build the program to be measurable from the start, see the guide to building a mentoring program.