# How can I calculate the defect leakage ratio?

3.0K    Asked by Anil Mer in QA Testing , Asked on Apr 26, 2022

I have few doubts in the Defect leakage ratio calculation formula.

I found one of the formula to calculate as below: CD=No. of Defects raise by customer after release

DR=No. of Defects raised by Tester before release

ID- No. of invalid Defects from Defects raised by tester before release(Eg. Duplicate, CannotFix, error in test environment etc.)

Formula to calculate Defect Leakage Defect Leakage=(CD/DR-ID)*100

Here my doubt is related to the period to consider and category of bugs found. Eg:- Release1 happened on April 27th 2018 and Release2 happened on Sep 24th 2018. Now to calculate Defect leakage ratio for Release2: What duration has to be considered?

For DR and ID, it is April 28th 2018 to Sep 24th 2018 and defections found internally in this duration. For CD, what needs to be considered from Sep 25th 2018 to till current Date? It won't be the Release2 Production leakage till the next release whatever production bugs are raised. If yes, then when exactly the metric will be calculated?

Another doubt is, if one production bug raised after Sep 25th 2018(After Release2) and the developer found the issue exists from the old releases say Release1 then whether one needs to consider this bug in the Release2 defect leakage ratio?

Answered by Anisha Dalal

The DLR for the current release is a changing metric that will increase over time until the release is closed.

The bug that was found by the customer in the latest release and reported by the tester in the previous release counts as a DR in the earlier release and a CD in the later release. With that said, the Defect Leakage Ratio as a number isn't nearly as useful as a list of bugs found by the customer, per release. This list demonstrates the delta between what the company thought the customer wanted and what the customer actually wanted. It doesn't matter if the bug was found internally or not; if the customer finds it the customer cares about it as the company didn't understand the importance of that thing the customer finds significant. Such a list reviewed by Developers, Testers, PMs and Management on a regular basis is a customer feedback loop that helps the company build software that better aligns with the needs and wants of the customer. This list will help the company gain better customer focus than a mere ratio.