--- title: Apdex score description: Apdex measures user satisfaction with your services' response time as a single score from 0 to 1 in Coralogix APM. url: https://coralogix.com/docs/user-guides/apm-v2/features/apdex-score/ product: apm feature: APM Overview feature_id: apm-general feature_identifier: apm/apm-general last_updated: '2026-11-10' --- # Apdex score ## Overview Apdex (Application Performance Index) is a standardized metric that measures user satisfaction with a service's response time. It condenses a full latency distribution into a single score from 0 to 1, where 1 means every request felt fast and 0 means every request was slow or failed. Use it to: * **Turn raw latency into one number**: give your team and your stakeholders a single, standardized score to track user satisfaction and compare it across services and over time. * **Set a per-service expectation**: define the response time you consider acceptable for a service through its threshold, then measure real traffic against that target. * **Feed the health model**: let Apdex contribute to a service's overall state through the Apdex health policy. ## How it works Apdex is derived from a single target threshold, T, that represents the response time you consider acceptable for a service. Every request falls into one of three categories: * **Satisfied**: answered in T or less. * **Tolerating**: answered in more than T but no more than 4T. * **Frustrated**: slower than 4T, or errored regardless of how fast it returned. Satisfied requests count in full and tolerating requests count as half: ``` Apdex = (satisfied + tolerating / 2) / total requests ``` For example, with a threshold of 2 seconds, a request answered within 2 seconds is satisfied, one answered in 2 to 8 seconds is tolerating, and anything slower than 8 seconds - or any errored request - is frustrated. Coralogix maps the resulting score to five quality ratings: | Rating | Score | | ------------ | --------- | | Excellent | 0.94-1 | | Good | 0.85-0.94 | | Fair | 0.7-0.85 | | Poor | 0.5-0.7 | | Unacceptable | Below 0.5 | ## Apdex in APM Apdex applies to services that report server (incoming) spans. APM surfaces it in three places: * **Apdex card**: on a service's **Overview**, the Apdex card charts the score over your selected timeframe on a fixed 0 to 1 axis, with the quality bands shaded behind the line so you can read the rating at a glance. A **Threshold = *value*** pill on the card opens the Apdex threshold editor. Click a point on the trend to open the Apdex details; hold ⌘ (or Ctrl) and click to pin the tooltip. * **Apdex health policy**: Apdex feeds a service's overall [health](https://coralogix.com/docs/user-guides/apm-v2/features/service-health.md) state through a dedicated health policy, so a drop in satisfaction surfaces alongside the service's other signals. * **Apdex details panel**: open the panel from the Apdex card to review the score over time and the operations dragging it down, and to edit the threshold. See [Apdex details panel](#apdex-details-panel). [![The Apdex card on a service Overview: the score and rating, a Threshold pill, and the Apdex score charted over time against the quality bands.](/docs/assets/images/apdex-card-51b7d4ed3c82a34f0335fa13262ac013.webp)](https://coralogix.com/docs/assets/images/apdex-card-51b7d4ed3c82a34f0335fa13262ac013.webp) ### Apdex details panel Select **Apdex details** on a service's Apdex card to investigate the score. The panel opens over the drilldown and follows the same time range and comparison. Use **Copy link** in the panel toolbar to share a direct link to it; the panel and the threshold editor also restore from the URL when you reload. At the top it shows the current **Score** and rating and the **Threshold** it is measured against. Select **Edit threshold** to open the **Apdex threshold** editor, which lets you try a threshold before saving it: * **Effect on this service**: for a candidate threshold, the editor scores what the service *would* rate at that threshold against its current score, and shows the **Satisfied / Tolerating / Frustrated** split of requests at that value. * **Account default or override**: a service either uses the account default (**Using the account default**) or overrides it (**Overrides the account default**); **Reset to default** returns it to the account value. * **Latency vs. threshold**: a percentile chart with a **draggable handle** for setting the threshold against the service's real latency. The threshold is chosen from the service's recorded latency buckets. * **Apdex formula**: the editor shows the Apdex formula in a panel of its own, so you can see how the threshold drives the score as you try values. On first setup, the editor pre-fills a suggested default threshold - you can save it as-is without changing anything. Saving closes the editor and confirms the threshold it wrote. A changed threshold applies only to data received after the change - scores already recorded are not recalculated. * **Apdex breakdown over time**: a bar chart of how many requests fell into each satisfaction bucket over the selected range, so you can watch the mix shift. A **Stacked** / **Individual** toggle in the chart header switches between stacking the three buckets into one bar per interval and drawing them as separate bars; it opens on **Stacked**, and your choice travels in the panel's link, so a shared or saved view reopens the chart the same way. The legend labels the buckets against the current threshold - for a 0.5s threshold, **Satisfied ≤500ms**, **Tolerating 500-2000ms**, and **Frustrated >2000ms or error**. The Apdex **score** is drawn on a secondary axis fixed from 0 to 1, so you can read the bucket mix and the resulting score together. Event markers (annotations) appear on the chart, so you can line up a shift in the mix with a deployment or other event. * **Top impacting transactions**: the transactions with the largest impact on the service's Apdex, sorted worst-first. Each row shows the operation's **Name**, its **Apdex impact**, the **Trigger** and **Method**, **Requests** and their trend, and **Errors** and the error-rate trend. Use **Search operations** to find one by name, the **Top N** selector to limit the table to the highest-impact operations, and select a row to open its [transaction drilldown](https://coralogix.com/docs/user-guides/apm-v2/features/transactions.md). Select **Go to Transactions** to open the full [Transactions](https://coralogix.com/docs/user-guides/apm-v2/features/transactions.md) tab. When the service is healthy, the section opens with a success message confirming that no transaction needs attention, followed by the table as usual. The service counts as healthy when its score is Good or Excellent, fewer than 0.5% of requests fall into **Frustrated**, and no transaction has an Apdex impact higher than Low. [![The Apdex details panel: the score and threshold, the Apdex breakdown over time chart, and the Top impacting transactions table.](/docs/assets/images/apdex-details-8e55864e1e836eb7d0da21777cf1745c.webp)](https://coralogix.com/docs/assets/images/apdex-details-8e55864e1e836eb7d0da21777cf1745c.webp) ## When Apdex cannot be calculated Apdex is computed from your span metrics' latency histogram, so the score exists only when the histogram includes buckets at both the threshold (`le=T`) and its 4× counterpart (`le=4T`). If either bucket is missing, the Apdex card cannot run the calculation and shows an empty state in place of a score. To resolve this, configure your collector so both `T` and `4T` are present in the bucket list. For the full setup, see [Apdex settings](https://coralogix.com/docs/user-guides/apm-v2/getting-started/span-metrics-recommended-configuration.md#apdex-settings) under Span Metrics configuration. ## Next steps Overlay deployments and configuration changes on your charts with [Annotations](https://coralogix.com/docs/user-guides/apm-v2/features/annotations.md). ## Additional resources | | | | ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Documentation | [APM](https://coralogix.com/docs/user-guides/apm-v2/getting-started/apm-onboarding-tutorial.md)
[Catalog](https://coralogix.com/docs/user-guides/apm-v2/services.md) | | Blogs | [Apdex Score: Calculation, Pros/Cons & 5 Ways to Improve Yours - Coralogix](https://coralogix.com/guides/real-user-monitoring/apdex-score/) |