What is the sweet spot when asking for a raise?

My first review is coming up soon! I recently graduated from college and started work as an engineer.

My entire team is filled with hard workers, but I feel that I have already taken on roles and responsibilities outside of my own. I have many examples of how I have directly impacted the bottom line and even taken on a supervisory role for certain projects. My manager also put me in charge of a specific process where I am responsible for giving tasks and assignments to my coworkers. I am not meaning to sound arrogant, but instead prefacing this question by explaining that I am not just asking for a raise at my first review out of the blue. I really have been working above and beyond my role and expectations and have already done a lot for the company that I feel would warrant a raise.

My question is what is the correct amount to ask for raise wise? As a company baseline, one of my coworkers who has been with the company for around 2 years received an 8 percent raise after his first year and experienced another raise with a promotion a couple of months ago and will probably receive another with reviews from our manager coming up.

I currently make around 70K and would really like to make around 80K. This would be around a 14% raise. I am scared that this would be asking too much. I do feel I’ve earned a raise, but I don’t really know how much. I am fresh out of college and really don’t know how raises and salary negotiation work.

What is too much or too little? How do I ask?