osCommerce Weight Base Shipping

In default osCommerce zone based shipping module supports only weight base shipping. If weight is zero then free shipping.
If someone want the shipping should be applied on the products attribute then he should go with osCommerce contribution. The osCommerce weight-based shipping module uses the simple formula to calculate the shipping which is

1:2.5 == shipping cost is $2.50 per kilogram

in weight based shipping, shipping applied as per the product weight if product weight is zero then shipping is also zero i.e. free shipping. If product has no weight and attribute have weight then no charges will be applied on that attribute weight.

osCommerce contribution

The contribution will alter not only the product price but it will also alter the product weight. This contribution gives the facility to assign weight to the product attribute which is added to the product actual weight to calculate total shipping cost. It uses the following formula.

Product weight = Product actual weight + Product attribute weight

It will then apply the shipping charges on that recalculated weight.
Recommended osCommerce contribution: http: //addons.oscommerce.com/info/1622