person Author: Process Fellows
The difference lies mainly in their strategic relevance and purpose.

Metric
A metric is a measurable value used to quantify a specific aspect and then typically used to track and monitor this aspect. For example metrics can be process / activity oriented, or they can be used to measure a product characteristic. Metrics provide data and help you understand what is happening.

• They can be operational, tactical, or analytical.
• Not every metric is critical for strategic success.
• Metrics answer the question: “What is going on?”

Examples of metrics:

• Website visits
• Number of support tickets
• Production cycle time
• Employee training hours
• SW defect density (#defects/ #lines of code)

KPI (Key Performance Indicator)
A KPI is a specific type of metric that is directly linked to a strategic objective. KPIs measure how effectively an organization is achieving its key business goals.

• All KPIs are metrics.
• Not all metrics are KPIs.
• KPIs answer the question: “Are we achieving our strategic goals?”

Example
Imagine a company whose strategic goal is to increase customer satisfaction.

• Metric: Average response time of customer support
• Metric: Number of resolved tickets
• KPI: Customer Satisfaction Score (CSAT) with a target of 90%

Why?
The response time and resolved tickets are useful metrics. However, the CSAT score is the KPI because it directly measures whether the strategic objective (improving customer satisfaction) is being achieved.

Simple Summary
Metric = Any measurable value
KPI = A strategically important metric tied to a business goal

In short: A KPI is a metric that matters most.