Dealing with startups' valuation - one should be familiar with two important concepts - Pre-Money and Post-Money.

Pre-money valuation refers to a company's value, not including external funding or the latest funding round. On the other hand, post-money refers to how much the company is worth after receiving the money and investments into it.

The Pre-Money and Post-Money Valuation Calculator help calculate the pre-money value and the post-money value, given the amount of money an investor invests (the investment) and the equity's proportion he gets for the investment.