Thomson Reuters
Shoppers walk a connecting path from The Court to The Plaza at the King of Prussia Mall, United State's largest retail shopping space, in King of Prussia, Pennsylvania on December 6, 2014.
That was the best reading since September 2015.
Economists had forecast that the index was little changed compared to July at 97, according to Bloomberg.
Consumers' outlook for the labor market and current business conditions improved compared to July. The share of people saying jobs were plentiful increased from 23% to 26%, the highest since January 2008.
"We expect consumer spending to remain the key driver of domestic demand, albeit at a more moderate pace than the robust 4.4 percent annualized rate registered in Q2," said Wells Fargo's Sam Bullard in a preview.