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About this tool
Calculate an Apdex score from satisfied, tolerating and frustrated request counts, with the rating band and the fixes needed to reach a target.
This calculator computes an Apdex (Application Performance Index) score — (satisfied + tolerating ÷ 2) ÷ total samples — the standardised 0-to-1 user-satisfaction metric defined by the Apdex Alliance specification and reported by New Relic, Datadog and most APM tools. Enter the satisfied, tolerating and frustrated request counts from your monitoring window and get the score, its rating band, and the cheapest set of request fixes that lifts you to a target.
Open Apdex Score Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Uses the Apdex Alliance definition — tolerating counts half, frustrated counts zero, and the tolerating ceiling is fixed at 4T.
Maps the score to the standard bands: Excellent ≥ 0.94, Good 0.85–0.93, Fair 0.70–0.84, Poor 0.50–0.69, Unacceptable below 0.50.
Shows the minimum number of frustrated and tolerating requests to repair to reach any target score, using their exact 1 and ½ weights.
Apdex = (satisfied requests + tolerating requests ÷ 2) ÷ total requests. Against a chosen target time T, requests at or under T are satisfied, those between T and 4T are tolerating (worth half), and those over 4T — or errored — are frustrated (worth nothing). 800 satisfied, 150 tolerating and 50 frustrated out of 1,000 gives (800 + 75) ÷ 1,000 = 0.875.
By the commonly used bands, 0.94 and above is Excellent, 0.85–0.93 is Good, 0.70–0.84 is Fair, 0.50–0.69 is Poor and anything below 0.50 is Unacceptable. Many teams set their alerting threshold in the 0.85–0.94 range, but the score is only meaningful relative to the T value it was measured against.
The factor of 4 is fixed by the Apdex Technical Specification so that scores are comparable across tools — you choose only T, the response time users find satisfying. With T = 0.5 s, requests up to 2 s count as tolerating and anything slower (or an error) counts as frustrated.
No — the score is defined relative to its target time, so 0.90 at T = 0.1 s reflects a far stricter standard than 0.90 at T = 2 s. Compare services either by aligning them on the same T or by tracking each service's own score over time; treat the number as an informational index, not a universal grade.
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