USPS Shipping charge calculation, many items = less accuracy

[Olof Holte]

Greetings honorable Zen Masters,

I am the owner of a Zen online store, not the Webmaster, but I do know my around the Admin, as well as, maybe better than the WM. I have the Zen Cart book and have read the shipping chapter.
Zen Cart 1.3.8a
v1.3.8 [2008-07-03 08:42:34] (Version Update 1.3.7->1.3.8)
v1.3.7 [2008-07-03 08:40:21] (Version Update 1.3.6->1.3.7)
v1.3.6 [2008-07-03 08:39:00] (Version Update 1.3.5->1.3.6)
v1.3.5 [2008-07-03 08:37:29] (Version Update 1.3.0.2->1.3.5)
v1.3.0.2 [2006-07-01 12:27:21] (Version Update 1.3.0.1->1.3.0.2)
v1.3.0.1 [2006-04-25 09:34:29] (Version Update 1.3.0->1.3.0.1)
v1.3.0 [2006-03-31 13:12:29] (Version Update 1.2.7->1.3.0)
v1.2.7 [2006-02-19 10:08:18] (Fresh Installation)

I am running into some trouble with shipping calculations now that we offer so many diverse products. When we only had a few items and most orders were for one or two products at a time, shipping calculations were very accurate. Now that customers are placing orders for many items at a time the calculations are not accurate. Indeed, in some cases too much and not competitive at all.

I use the USPS shipping mod. I have 70 cents as “handling” to cover the Delivery Confirmation tag (tacking #) and offer most of the postal services; Priority Mail, 1st Class, Express and international.

Each product has a shipping weight based on the weight of the item and a very modest extra to cover the weight of the packaging need for that item. The shipping weight has been figured for each and every product by placing the product in an appropriate package, weighing it, rounding down, and then adjusted, if necessary, based on the real shipping cost at the post office.

I opted not to use the Package Tare config because of our diversity of product, as it seems to apply the same ratio, universally to all items.

For example; We sell anchors that have a package weight to product ratio of about 1:10 and sponges that have a package weight to product ratio of about 10:1. I could split the difference down the middle, but I have so many products of all kinds of densities, and an ever-changing popularity from one product to another, that it is hard to come up with a ratio that is durable and not arbitrary. According to my best “calculations” average packaging weight is about 91% of product weight and this cannot be true. My average shipping cost is about 10% of purchase price, and this I know to be true and accurate. If I were to base shipping rates on this % it will make sponge customers pay extra and anchor customers pay less for shipping.

If I were to use the use the Package Tare config I believe I would have the same results, but less accuracy, due to a universal ratio, applied to products of diverse density and different packaging needs.

When a customer orders one item from our shop the shipping is highly accurate. When a customer orders a dozen or so different items the shipping rate climbs much higher than it actually cost to mail, the more items, same or different, the less accurate. I also sell rope and have had to find the average length purchased to base the shipping weight on that, but it penalizes any buyer who wishes to purchase more than the average amount, and rewards those who purchase less than average.

I make a “shipping adjustment” to customers who have paid too much for shipping, as a refund. I never ask for more than the cart has calculated. Yes, this is nice to refund them, but it does not help the customer who is deciding to make a purchase or not, to buy from me, rather than another shop, even though this policy is spelled out on the FAQ page. Refunding “shipping adjustments” takes time too.

Then there is the fairly new dimensional weight charges for USPS parcels over one cubic foot. If I have a bulky product, even a light weight one, like a life vest, with the correct shipping weight, the cost to mail it will be more than the customer pays to have it shipped. I have added to the weight of some of those bulky products, but this makes 2 life vests cost much more than is actually paid for at the post office.

Is there anything in the works for dimensional properties of products? There seems to be no place to enter dims for a product. And, is there a USPS config that will plug into USPS with package dims. Yes, I know this could be very complex.

I am planning on looking into a UPS mod, but would imagine that I would face the same set of problems. I am also considering a “free shipping” break at some purchase price level, but that would simply be a “bad-aide”, as I may want to charge shipping for something that is over a certain cost.

I do not have any qualms about absorbing some shipping costs, neither do I seek to profit on shipping. I do not think that customers expect to pay less than what it actually costs to ship the parcel, but of course they have no idea, and shipping cost at checkout is all they are interested in. They do not want to pay more than what the shipping actually cost either. I just want to find a happy medium that is fair to all.

I would like to ship kayaks at some time in the future and this may take an entirely different set of shipping rules and parcel carrier. I am not asking about this yet, but I can see a day where I have to ship everything from a 1-inch washer to a 17-foot kayak.

What I would like to see is some sort of way the shipping weight could be reduced by a percentage depending on how many items are in the order. Maybe reduced by R% for 5 items, 2xR% for 10 items, 3xR% for 15 items, and so forth. (R=shipping Reduction) Or maybe apply the something similar to the Package Tare config. Because the weight of the box that is used to ship one item is not that much less than the weight of a box to ship four items.

Please help me to find a solution honorable Zen Masters.