Anyone have good tips for how to quickly figure out which carrier will offer the lowest shipping rate based on weight, destination, and speed?

Don't forget DIM weight (heavier weight assigned based on size versus actual weight) as a factor as well.

Also, most folks find it is not best to do it on a package by package basis. The reason being that small shippers will want to choose a carrier and give them all their shipment volume in return for an across-the-board rate discount. I'm not saying per-package carrier selection can't be done, just that it will almost always be more economical to make an overall choice and get the best discount you can get (rather than splitting your volume across 2-3-4 carriers).

Part if the reasoning is that in general you can say next-day is next-day, whether it arrives at 10am or Noon and the same goes for any other class of service. And since each carriers' zones (and thus rates) will vary from the competition, it makes little sense to go through the exercise of finding cheapest for every single package. You'll save more by making your overall selection and applying your total volume to get the best possible discount.

If you've got plenty of volume, you can start slicing things more finely and pick one carrier for Next-day, one for ground and one for international. However, most of us around here don't have that kind of volume yet.

BTW, when negotiating overall rates if you feel UPS and FedEx (and even DHL) are on par for service, go ahead and negotiate with both. Just remember only one will get the volume (otherwise your rates will be raised pronto).

I hope that helps,
Ed

For USPS Priority Mail vs UPS Ground (the 2 I use)

If it's less than 2 pounds, then USPS

Greater than or equal to 2 pounds, UPS

Any destination applies, but speed depends on where you are shipping from

Is this the kind of thing you are looking for?