# Thread: USPS shipping module / tare weight

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## USPS shipping module / tare weight

This tare weight is driving me nuts.

zen cart version 1.3.8a

Goal: Set up USPS shipping module using tare weight so multiple orders in the same session do not compound packaging materials weight

IE: I want to set it up so that the tare weight is added only one time into a total multiple purchase weight.

My average packing supply weight is about 7oz or .4375

When I add a product to the catalog I enter its actual weight, not the packaged weight.

I have my product weight entered as pounds and ounces in the decimal point system.

IE:

Book 1 weighs 10 oz = .625
Book 2 weighs 6 oz = .375
Book 3 weighs 1lb 6oz = 1.375
total weight 2lbs 6oz = 2.375

I test the shopping cart for product weight calculation per item.

I add a book to the shopping cart. Above the item it shows how many items and the how much it weighs.
The weight shows correctly. I add the other two books to the cart, one at a time to see if the weight is calculated correctly for each addition. The weight is correct for each addition.

In shipping/packaging > the "Small to Medium - added percentage:weight", I'm thinking to set a percentage figure with weight set at 0 is the way to accomplish what I want. I have tried adjusting the percentage weight until the cart shipping estimator total lines up with USPS website calculations.
This worked until I added in a third book and then the tare weight goes higher than expected. So I back the tare percentage down until it again lines up with USPS website calc.

The problem is when I add just one book to the cart I get offered first class mailing when I know once packaged it will be too heavy for 1st class.

I hope this explanation makes sense. Anyway with the weight figures I've given and my goals what should I be doing with the tare to get things correct?

Has anyone else had success with this?
Last edited by buildingblocks; 13 Oct 2008 at 07:29 PM.

2. ## Re: USPS shipping module / tare weight

If I set the Tare to 0:3 then I add 3 lbs to the Total weight of the Order ... not per product ...

What are your settings in the Configuration ... Shipping/Packaging ...

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## Re: USPS shipping module / tare weight

>>
What are your settings in the Configuration ... Shipping/Packaging ...<<

Package Tare Small to Medium - added percentage:weight 35:0

4. ## Re: USPS shipping module / tare weight

Book 1 weighs 10 oz = .625
Book 2 weighs 6 oz = .375
Book 3 weighs 1lb 6oz = 1.375
total weight 2lbs 6oz = 2.375

2lbs 6oz is more than 13oz ...

13 oz is 0.8125 ...

.625 + 35% is 0.84375
.375 + 35% is 0.50625
1.375 +35% is 1.85625

Kinda makes it hard to keep in the 13oz rule with that Tare setting ...

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## Re: USPS shipping module / tare weight

>>Kinda makes it hard to keep in the 13oz rule with that Tare setting ... <<

It sure does.

Suggestions welcome from anyone who worked something out along the lines of what I'm trying to do.

6. ## Re: USPS shipping module / tare weight

Set the Tare to 0:0 and there isn't a Tare added ...

Do you need the Tare weight? Or, could you manage it with a Handling charge?

Or can you explain better when you do or don't need a Tare Weight added?

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## Re: USPS shipping module / tare weight

I sell books.

The tare is to account for the average weight of packing materials used to ship one book.

for instance:

A packaged book weighs 1lb 3oz. Shipping by media mail.

The Media mail rate for a package weighing over 1lb but not over 2lbs will cost \$2.58.

Another paperback or two may be able to ship in that same package at the same rate providing the weight does not go over 2lbs

I need to be able to charge for just one container weight.

If a buyer purchases 3 books in one order I don't want them to be charged a shipping weight for 3 container weights.

8. ## Re: USPS shipping module / tare weight

I am not sure where you are getting the 3 package Tare weights ...

You take an order of 7 lbs and add a 3 lb Tare ...

If the order is made up of
1 Product A @ 2lbs = 2lb
4 Product B @ .25lb = 1lb
1 Product C @ 4lb = 4lb
Total weight 7lb + 3lb Tare = 10lbs

There is just one Tare applied here ...

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## Re: USPS shipping module / tare weight

Sorry if my explanations are confusing.

I'm still trying to understand how this is working and maybe I'm not getting it.

This

>>I am not sure where you are getting the 3 package Tare weights ...<<

comes from

if I don't do the tare as a percentage, but instead do it as weight, 0:3 for example , then the tare weight would be added to each item in a multiple purchase?

Just when I think it's coming clear I'm confuzzled again

10. ## Re: USPS shipping module / tare weight

I set the Tare to 0:3 which adds 3lbs ...

I add to the order a Product at 1lb and will get 4lbs ...

I add 2 of the same Product to the order and get 2 x 1lb = 2lb + 3lb = 5lbs ...

I add 3 Products of varying weight to the order in varying quantity ...

I put them all on the Weight Scale and it comes out to 12lbs ... then I add a 3lb Tare to that for 15lbs ...

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