[sarvesh]

With shipping calculation there is usually two options you can use FedEx or UPS provided standard size boxes or you can use your own boxes. The latter option is what you are looking at for your problem. The bare minimum information you need about the shipping item is weight. FedEx and UPS both return your rates if you give their API the weight and addresses.

As for calculating the number boxes you will need to do that based on how your warehouse is gonna ship these products. This is the hardest part. Most people usually maintain the dimensions of the actual product. Based on this and how you plan to ship them you will need to figure the number of boxes. The shipping rates that you have negotiated with UPS/FedEx is usually a little lower than what the user will see, so this more often than not should cover your extra costs that you may incur.

Although calculating the number of boxes and their dimension is a little involved it gives you more accuracy. Which is better for you and your customer.