You put the actual dimensions and weight. Whichever cost is higher, dimensional weight or actual weight, that's what it costs. More on reddit.com

Any issues or concerns should be ... official UPS Customer Service. ... I am looking for a formula to calculate the shipping cost from location to location world wide with based on dimensions. Can anyone help? ... Archived post. New comments cannot be posted and votes cannot be cast. ... Create your account and connect with a world of communities. ... By continuing, ... More on reddit.com

I've found the calculator to be very accurate (for both UPS and FedEx) IF you measure & weigh correctly. UPS was only added to eBay fairly recently and I've been auditing my shipments exactly to ensure no upcharge 'gotchas'. So far entirely accurate. By 'measuring correctly' I mean realize that 37.01" x 19.01" x 2.01" and 11.01 lbs should be entered as 38x20x3 @ 12 lbs. Similarly, be careful of 'irregular' sizes: if your package is 38x20 but one end is 3" high and the other is 2" high, that's 38x20x3 - you don't take the 'average' or anything. Another 'gotcha' is if you buy or get boxes with the 'size' printed on them, that's the INTERNAL dimensions. So if you take a box that says "12x12x12" and ship it using "12x12x12" as the dimensions, you're likely to get hit with an 'upcharge' for a 13x13x13 box... Also realize that the UPS charges the greater-of actual weight or 'dimensional' weight (based on size). So if a 0.1" or 0.1 lb difference you didn't include puts you from one into the other, charges can go up notably: basically you're jumping to a higher rate-tier. Also, if you ship a box that ends up bigger or heavier than UPS Ground actually handles, there's not just higher shipping fees, but a 'penalty' fee as well... So if you're mailing a box that's 149.9lb make DAMNED sure your scale is accurate, because if it's actually 150.1 lbs, you could face some SERIOUS upcharges. Given all the above, I've found IF you put in the truly-correct information, the calculated cost is very accurate. There do seem to be some legit horror-stories about folks getting whacked with completely overstated charges. But MOST of the ones I've seen where real info eventually got provided, it turned out to be mismeasurement and/or 'hoping to slide one by'... More on reddit.com

I have a macro that I use to ship packages via USPS which does a direct query to the USPS rate servers. It requires registering an account with USPS. It won't help you with UPS, but if you could use this, post a msg and I'll post it here. More on reddit.com