What is the formula for calculating the expanded area of whole-house customization?

The expanded area is calculated by breaking the cabinet body apart: add up the visible area of all panels, including side panels, top and bottom panels, shelves, back panels, door panels, etc., accumulating length times width for each panel, then multiply by the panel unit price. It is more detailed than the projected area, but the numbers change whenever the internal layout of the cabinet changes, so it must be calculated against the drawings, and that is how we do it as well. For kitchen cabinets, pricing is by linear metre: basic configuration E0 particle board cabinet body + PET door, Beijing 900–1,000 yuan/linear metre, Baoding, Langfang, Xiong'an and Zhuozhou areas 765–850 yuan/linear metre; mainstream configuration ENF particle board cabinet body + PET door, Beijing 1,020–1,250 yuan/linear metre, Baoding, Langfang, Xiong'an and Zhuozhou areas 867–1,062.5 yuan/linear metre; upgraded configuration ENF eco board cabinet body + PET door, Beijing 1,300–1,650 yuan/linear metre, Baoding, Langfang, Xiong'an and Zhuozhou areas 1,105–1,402.5 yuan/linear metre. The above are reference prices and do not constitute a formal quotation; actual projects require further calculation based on dimensions, design, materials, hardware, quantity and site conditions.