How can I have an idea of the dilution of employee stock options for a company that is going through different rounds of funding?
For example, a company that has received a total of $100M funding up until now gives stock options at the moment of signing a new employee, always for the same valuation amount. Let's suppose they give $1000 worth in stock options at the moment of signing over 3 years in batches of 6 months. Let's suppose that after a while, they go through another round of funding of another $50M and they sign new employees and give them the same $1000 worth of stock options, but now a different amount, given that the company has received more funding since last time around, and the pre-IPO valuation by the same company may have changed.
How can one calculate the ratio of dilution vs valuation between these two rounds in the stock options?