Based on the Agile Principles, "Working software is the primary measure of progress". You can replace "working software" with "releasable product" to apply it to every kind of project.
The main guideline is that you should not distract yourself by the abstract performance factors that are not directly linked to the project goals; e.g. actual man-hours spent on the project, or the lines of code written are completely work-based measurements that are not useful.
Fortunately, PRINCE2 originally insists on a very productive way of measuring progress that is applicable to Agile projects as well as predictive ones, and not many changes are required here.
The main differences in Agile environments are:
- Measurements are usually simpler, because they are based on independent backlog items rather than complex schedules.
- Reporting is usually simpler, based on Information Radiators rather than documents.
It's important to mention that when you're using PRINCE2 Agile, you're expected to have a complete, multiple-level progress measurement system that shows the performance in the delivery, release, stage, and project levels.
- Progress Theme at PRINCE2 wiki