How is the mill rate calculated?

Simply put it is a math equation. The Town’s Budget (funds the Town needs to operate) divided by the Town’s net Grand List (all of the assessments RE, PP, MV). If everyone’s assessment is decreased the mill rate will increase. The opposite is true if all assessments are increased the mill rate decreases. The Town sets the mill rate to an amount that will allow the Town to collect the revenue it needs to operate the Town.