Carpet pad cost: $0.30 to $0.60 sq/ft. Carpet installation cost: $0.50 sq/ft. For budgeting purposes, adding $1.00 sq/ft. for padding and installation to the carpet cost gives a good estimate. Captain’s parting words: There’s no exact answer for how much carpet costs.Nevertheless, it’s important to have an idea of what you should be paying.arpet installation cost: $0.50 sq/ft. For budgeting purposes, adding $1.00 sq/ft. for padding and installation to the carpet cost gives a good estimate. Captain’s parting words: There’s no exact answer for how much carpet costs. Nevertheless, it’s important to have an idea of what you should be paying.