If you service items like rugs, carpets or curtains which you price per square meter/feet, then you will need to ensure that you select the relevant product type for these items when you add or edit a product.

As indicated below, you can find the price per square meter/feet in the drop-down under 'Product Type'.

When you then add this product with this product type, you can go to NEW ORDER.

On the NEW ORDER page, select this product where you will then be able to enter the dimensions for the width and height to get the total price as evidenced below.