How do you measure testing effort?

A common rule of thumb is to allocate about 20-30% of the overall development time to QA activities. (Waterfall model)

OR

If you are embedding QA people in your teams so that they are testing simultaneously with the developers then the rule of thumb of 1 QA person for every 4-5 developers is common. (Agile)

This is the biggest misconception we still have concerning the estimations of QA efforts.

So as a QA lead, or QA person you have to justify your efforts most of the time.

QA estimations and allocation must be done considering below points :

1. Time - How much time testing will take?
2. Team Count- How many QA members are required?
3. Cost - What will be the overall testing cost?
4. Skills - What shall be the skill set of the QA team?

There is no accurate way to predict QA effort using a model based on estimated Development effort. Estimating the percentage of overall development time that should be dedicated to Quality Assurance (QA) can vary depending on the project, team, and industry and can fluctuate based on factors such as project complexity, size, and criticality. It's important to consider the specific needs of each project and adjust the allocation accordingly. For example, if you are testing a mobile application and say the development effort is 50 days. Now you can not take 30% of the development effort for testing. You may want to consider several devices you want to test, different OSs (Android, iOS, etc.).

Even if your testing effort is more than development efforts, do not hesitate to invest. In conclusion, if you want your customers to have a ‘WOW’ experience you should decide smartly how much to test without impacting on business/budget.?