Latency Percentile Calculator
Paste numbers in any unit, separated by spaces, commas or newlines. Straight from a log or a spreadsheet column is fine.
Paste samples above to see P50 through P99.9, min, mean and max.
Paste samples straight from a log and read the percentiles that matter.
Latency percentile FAQs
Why use percentiles instead of the average?
Averages hide the users having a bad time. A service can average 100ms while one request in fifty takes three seconds, and those are the requests people remember. P50 describes the typical experience, P99 describes the worst one in a hundred, and both matter.
What does P99 mean exactly?
99% of sampled requests completed at or below that value. If P99 is 800ms, one request in a hundred took longer. At scale that is a lot of requests: a million requests a day means ten thousand of them beyond P99.
How many samples do I need for a trustworthy P99?
As a rule of thumb, at least a few hundred for P99 and a few thousand for P99.9. With ten samples, the top percentiles are just your maximum wearing a costume.
What is tail latency and why the warning?
The gap between typical and worst-case response times. When P99 is many multiples of the median, a minority of requests are taking a very different path: cold caches, garbage collection pauses, lock contention, or an overloaded dependency. The warning fires when P99 exceeds three times the median.
Is my data sent anywhere?
No. Samples are processed in your browser and the page works offline, which matters when the numbers come from production logs.