How do I calculate my pre-money valuation?

Pre-money valuation = issued shares (fully diluted) x price per share in this offering.

For example, ABC Corp currently has 5,000,000 shares of common stock issued.  It wants to raise $1,000,000 at $1 per share.  This means;

5,000,000 issued shares x $1/share = $5,000,000 pre-money valuation.

*This means that because the # of currently issued shares is a fixed # for your company, price per share & valuation are directly related (increasing one increases the other).