An overview of the general cost of living index for Lake Forest, IL is displayed above for your reference. Residents in Lake Forest, IL enjoy a cost of living index of 189. This index is 91% higher than the Illinois average, and 89% higher than the national average. The following categories are used when determining the cost of living index for any given city: health care (5%), transportation (9%), utilities (10%), groceries (13%), housing (30%), and goods/services (33%). Clearly, housing and goods/services make up the majority of the formula for calculating the cost of living index. Because of this, the general cost of living for any given area can be estimated by looking at the cost of everyday goods in that area. For those living in Lake Forest, IL, the average cost of goods and services is 14% higher than it is in Illinois, and it is 15% higher than the national average.