Defect Age

What is Defect Age?

Defect age measures the amount of time (or number of phases/builds) that elapses between when a defect is introduced and when it is discovered or fixed.

Ways to Measure Defect Age

• Time-based: The number of days between defect introduction and discovery/resolution.
• Phase-based: The number of development phases the defect has passed through undetected (e.g., introduced in design, found in system testing).

Why Defect Age Matters

Older defects — those that persist through multiple phases before being found — are generally more expensive to fix and often indicate weaknesses in earlier testing or review activities. Tracking defect age helps teams identify where to strengthen their processes.