Science of wrapping presents

I was delighted to read in the Metro newspaper that a researcher at Leicester University has devised an eco-friendly scientific formula on how to wrap a Christmas present. Apparently most of us overestimate the amount of paper we need to wrap up Christmas presents. However, mathematician Warwick Dumas has been working with Bluewater to devise the perfect method of gift-wrapping to help customers save time and money and reduce the amount of paper that will be wasted. The length of the wrapping paper should be as long as the perimeter of the side of the gift, with no more than 2cm allowed for an overlap and the width should be just a little over the sum of the width and the depth of the gift. Mathematically, this can be expressed as A1 = 2(ab+ac+bc+c2).