USPS Rounding Errors -- Should never round down

[TraderDan]

Anybody...?

[TraderDan]

So no admins actually care that the USPS Shipping Module simply does NOT function correctly? Say it ain't so.....

[Ajeh]

Google says ...
0.482 pounds = 7.71200 ounces

0.452 pounds = 7.23200 ounces

Could you also post your Ship From and Ship To so we are comparing apples and apples?

[TraderDan]

Ajeh, you're right about what Google says, 0.452 lbs is 7.232 ounces... a typo in my post, but it doesn't actually change anything. It's over 7 ounces, therefore USPS will automatically charge you at the 8-ounce rate, which for 1st Class Mail would be $2.41. And it's still apples to apples since USPS First Class Mail isn't determines by zip code.

So you see, it shouldn't matter whether my package weighs 7.712 or 7.232 ounces, either way ZC should calculate the shipping charge based on 8-ounces. Unfortunately, this doesn't appear to be what's happening.

Instead, it assigns the correct $2.41 charge to the package weighing 7.781, which I assume is because, simply enough, the routine correctly rounded up to 8.000. But then ZC only assigns a $2.24 charge (the USPS 7-ounce rate) to the package weighing 7.232, even though the USPS requires that I ship it at the 8-ounce rate. Here I suspect it's just a matter of the Shipping Module rounding down from 7.232 when in fact it should still round up to 8.000 as well.

If it were up to me and I knew where exactly I could tweak the code, I'd make it so the module would round up for anything that's, say, 0.050 over the full-ounce mark.


Did that all make sense?

[Ajeh]

Look in the usps.php shipping module and tweak the calculation on the pounds and ounces to the way you want it to work ...

We will look further into this for a future release ...

[Ajeh]

Edit your usps.php shipping module and change:

    $shipping_ounces = round(16 * ($usps_shipping_weight - floor($usps_shipping_weight)));

to read:

    $shipping_ounces = (16 * ($usps_shipping_weight - floor($usps_shipping_weight)));

Do you get more accurate rates now?

[TraderDan]

Ajeh-

Thanks for taking the time to help. It's been a while since my initial posting (cra-zee busy these days), but I have just implemented the suggested change and will let you know.

And since we're on the topic of the USPS shipping module, I have another related question... why is ZC insisting that a 1-ounce package shipped to Canada cost $20 USPS Priority International?!

I have both First-Class Mail International and Priority Mail International enabled in my module, but even for a 1-ounce package it is coming up with a $20 Priority charge ONLY. Any insight would be greatly appreciated... again.

Thanks in advance,
-Dan

[TraderDan]

Edit your usps.php shipping module and change:

    $shipping_ounces = round(16 * ($usps_shipping_weight - floor($usps_shipping_weight)));

to read:

    $shipping_ounces = (16 * ($usps_shipping_weight - floor($usps_shipping_weight)));

Do you get more accurate rates now?

Unfortunately, this does not fix the problem, it only makes it worse actually. After observing the differences, it's clear that the suggested edit above causes everything to round down. For example, I just had a package that weighs 6.7 ounces and ZC now decided to charge for only 6 ounces, which means I'm losing money. When I changed it back though, it properly calculated the shipping for 7 ounces.

So yeah, there's still some real issues going on here with the USPS module... hoping these can get resolved for a future release.

[Kirsten5]

So no admins actually care that the USPS Shipping Module simply does NOT function correctly? Say it ain't so.....

[Ajeh]

TraderDan, that is still not the right file ...

If you edit the file, you will see it contains on line 3:

* USPS Module for Zen Cart v1.3.x, revised May 12, 2008 for new USPS rates effective May 12, 2008

And that the ID on line 9 is:

* @version $Id: usps.php 8516 2008-05-13 01:56:07Z drbyte $

Get the USPS May 12 2008 download and load it to the directory:
/includes/modules/shipping

If you then search it and get the wrong date, delete the file on the server ... and then load it ...