Shipping Calculations Off.

I am using UPS for domestic shipping and USPS for international shipping. I have set up the weight and dimensions for each product. But, when I get an order the shipping cost is way off. For instance I had a customer order a product and was charged $180 for shipping. I know this is true because I got the email for the order with $180 in shipping. When I logged on to place an order for the same item with his account, it gave me a shipping cost of $15. I am getting shipping estimates from both UPS and USPS ranging from $5 plus off. I only have a $3 handling charge, but being off of more than $10 is a bit much.

Am I the only one having this problem?

I am getting a lot of questions about shipping and I am having to go through every order to correct the shipping cost.

I'm seeing something like this, but for Canada Post. When i compare the rates form the site VS what my dev site calculates there's a difference. I wonder if a discount is being applied.

I do not think nopCommerce get the fuel surcharge or adds any insurance on to the freight quote. So, I under stand it being off a little. My problem is it is off a lot. I did find that the size entered in can cause a lot if issue. I have one product that is 4.75" x x 4.25" x 3.75" shipping size. If I order ten the shipping is over $60 when is should be less than $20. If I set the size to 0 then the shipping comes out a little lower than what it should be.

When you site gets a quote for shipping, it is at your cost. For instance UPS give a shipping estimate of what you account with its discount and not the price quote off their website.

I have found that if I remove all of the dimensions from the variant, then I get the right quote of shipping with my discount for having an account. I understand that it does not add any surcharges, like insurance, to the quoted price.

What I do not understand that if I have dimensions in the variant, and order more than one item the prices are way off. If I order 3 items that weight 10.5 lbs each and each have a dimension of 6" x 6" x 6", and have them shipped by USPS priority mail international to Australia. The price come out close, but if I ship 4 of them the price is off a little and if I ship 6 the price is cheaper than if I ship 4 of them. If I do not have any dimensions than the price is correct.