Defect Removal Efficiency
Defect Removal Efficiency (DRE) measures what percentage of total defects — those found during testing plus those found later in production — were actually caught before release. A DRE of 90% means 90% of all eventual defects were caught pre-release, and 10% escaped to production.
The formula is straightforward: defects found before release, divided by the total of defects found before release plus defects found after release (in a defined post-release window), expressed as a percentage — a single, comparable number summarizing how effective the entire testing process was at catching issues before users did.
DRE can only be calculated after the fact, once enough time has passed post-release to know how many defects actually escaped — which makes it a retrospective, trend-tracking metric rather than something usable for real-time decisions during an active release cycle.
