Min, Max, Mean, Average, P90, P95, and P99: What They Mean (and When to Use Them)
If you’ve ever looked at system metrics, API latency charts, or a performance report, you’ve probably seen a mix of terms like minimum, maximum, mean, average, and percentile values like p90, p95, and p99. They all describe “what the numbers look like,” but they answer different questions. Picking the wrong one can hide real problems—or make healthy systems look broken. This guide explains what each metric means, how to interpret it, and which one to use for common monitoring and reporting scenarios. A quick mental model Imagine you measure the response time for 10,000 requests over a minute. You now have a list of numbers (one per request). Summary statistics help you describe that list: Min/Max: the extremes Mean/Average: the center (one kind of “typical”) Percentiles (p90/p95/p99): “how bad it gets for the slowest X% of requests” Minimum (min) Definition: The smallest observed value. What it answers: “What’s the fastest