Help needed estimating value.

[Raymond Wiggins]

A few years ago I was looking to invest and I bought ten units in a small town just south of the Kansas City Metro area. I have improved them significantly and have raised the rent from an average of $950 per unit to about $1200 per unit. My wife and I are looking to move to the east coast and reinvest there. My problem is that I have no idea how to estimate the value of the units. I realize I should have known this before I bought, but here I am. Is there a simple metric I can use. Something like monthly rent minus taxes, insurance, and upkeep? Any help would be greatly appreciated.