How to use the Defect Density Calculator
- 1. Enter defectsType the number of defects found before release.
- 2. Enter sizeGive the size and unit: KLOC, function points, modules or story points.
- 3. Add production bugsOptionally add defects found after release to get DRE.
Formulas and worked example
- Defect density = defects ÷ size.
- Defect removal efficiency (DRE) = defects found before release ÷ (before + after release) × 100.
- Escaped defects = defects found after release ÷ size.
Example: testing finds 45 defects in a 15 KLOC (15,000 lines) module, so the density is 3 defects per KLOC. After launch, users report 5 more. DRE = 45 ÷ 50 = 90%, meaning testing caught nine of every ten known bugs.
Using the numbers wisely
Defect density helps compare modules within the same project: a module at 8 per KLOC next to others at 2 deserves a code review and extra regression tests. DRE tracks how well your process stops bugs over several releases.
- Count consistently. Decide whether duplicates, cosmetic bugs and rejected reports count, and stick to it.
- Lines of code vary by language, so do not compare a Python module with a Java one by KLOC.
- Function points measure size by functionality and compare better across languages.
- Do not use it to rank people. Developers will stop logging bugs, and the metric becomes useless.
There is no universal "good" density; compare with your own history. Track coverage alongside it with the test coverage calculator, and plan the effort for the next cycle with the test estimation calculator.
Frequently asked questions
What is KLOC?
Thousand lines of code. 15 KLOC means about 15,000 lines, usually counted without blank lines and comments.
Can DRE reach 100%?
Only if no defect is ever found after release, which is rare. DRE also changes as more production bugs are reported over time.
Is the Defect Density Calculator free?
Yes, the Defect Density Calculator is free. The first time you see your first result, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.