It's really hard to see yourself as others see you, even when you're trying your best to be open and objective. Any manager who has ever been blindsided with complaints from a subordinate, or an employee who has been struck by a poor evaluation from a superior knows how hard it is to judge yourself, by yourself. And that's where 360-degree feedback comes in.
360-degree feedback, also called multi-rater feedback or panoramic feedback, depends on evaluations from those all around you, hence the. This evaluation style doesn't just rely on a superior who judges your performance, but also draws in observations, opinions, and ratings from co-workers, subordinates, internal customers, external customers, and pretty much anyone who has contact with you regularly in a professional setting.
The format varies, depending on the company, your position, and which specific area you want feedback on, but often you will fill out a review form on yourself at the same time others are rating you. The feedback may be quantitative (numerical scores) and qualitative (narrative comments).
In the end, the results are compiled, and you learn where, and how much, difference lies between how you see yourself and how others rate your business performance.
Most 360 systems have extensive safeguards for anonymity and confidentiality. These features assure participants that 360-degree feedback is a safe way to share information that is hard to measure and awkward to communicate.
While 360 is an extremely effective diagnostic tool, don’t expect it to solve all your organization's performance improvement problems. In fact, don't expect it to do anything for you unless you use it as part of an overall development strategy. Keep in mind that 360 degree feedback is not intended to be used as a performance appraisal tool. Rather, it is best when used for developmental purposes.
Source: Beginner's Guide to Assessment & 360 FYI