As part of my offer package I'm offered stock options in a private company that was self sufficient for 8 years and almost didn't take any funding. For the last 3-4 years revenue numbers have been doubling each year. Approximate numbers: last year revenue was $50M with 20% profit margin, company has approximately 130 employees (100 engineers). Company took $10M funding 5 years ago, and there are no plans for funding rounds. Company plans to go public within 2-3 years.

What kind of rough valuation can be given to the company to approximate current stock option value? Obviously, valuation could be off by 10 times, still what's a general total value that can be given to the company now given the numbers provided? I have other offers from a couple of big companies (google, fb, etc) and my goal is to compare value of stock options in a private startup with sock bonuses in public company (e.g. I want to compare apples with oranges).