Value of Adding 3rd bedroom to rental property flip

[Debbie Olsen]

We are looking to flip a single family home in Livermore, CA  It is currently a 2/1 rental property.  We have the opportunity to add a 3rd bedroom, but don't know how to determine the valueadd to potential investor.  As a 2/1, the property currently rents for $1450.  The post reno rent would be $1800 (as a 2/1).  As a 3/1, the rent should jump to $2200-$2300.  Is there a rule of thumb/formula for calculating what the additional bedroom will add to the sale price?