Best way to find out what you're worth is to ask around at other companies and simply talk to your boss about what he thinks you are worth. Many people make the mistake of treating their company relationship like they would a personal one.
Example: early on in my career I was working for a company where I was clearly WAY below the average age. Most in my office were in their 50's and 60's with PhD's and here I was a new grad just trying to keep up. Loved the environment, learned A TON.
My first year I got a standard raise of 3.5% and was told that the company across the board gives this raise and that I fell right in the middle as a new employee. Some who were below average got 3% and others who were above got 4%. The next year, the same speech was given to me... this time the average raise being 4.5%.
I stressed myself for the next year about a way to approach my boss to tell him I thought I was worth more. Ultimately I came up with the following plan to say: "Look, I appreciate that the company has these average raises across the board, but I looked up online what someone who is really advanced in this field is making, like most of my older colleagues here that I'm learning from. My best guess is that their salaries are in the 150-175K range and I just wanted to ask if these 3-4% averages raises are putting me on track to be at that level relative to inflation by the time I'm as advanced as them? Also, don't younger employees typically advance in pay faster than they do later in their career?"
My boss being the engineer type he was, did some mental math and said "you are absolutely correct, a younger employee like you should be getting a larger raise early in your career. We want to make sure we stay competitive and don't lose you."
The next two years my raise was in the 7.5-9% range... about twice what the company average was
Can't hurt to ask.