Calculating net worth involves adding up all your assets and subtracting all your liabilities.  The resulting sum is your net worth.

The value of your primary residence is not included in your net worth calculation.  In addition, any mortgage or other loan on the residence does not count as a liability up to the fair market value of the residence.  If the loan is for more than the fair market value of the residence (i.e., if your mortgage is underwater), then the loan amount that is over the fair market value counts as a liability under the net worth test.

Further, any increase in the loan amount in the 60 days prior to your purchase of the securities (even if the loan amount does not exceed the value of the residence) will count as a liability as well.  The reason for this is to prevent net worth from being artificially inflated through converting home equity into cash or other assets.

The following table sets forth examples of calculations under the net worth test for being an accredited investor:

References: