If UPS, when the weight per carton, ship from/to zip codes, selection of shipping transit time, etc., the shipping charges can be arrived at with a close estimate, also adding in the weight of the shipping carton(s) and packing material.
Multiple cartons cost more to ship with the same grand total weight than fewer cartons. As an example, 2 cartons @ 20 lbs ea will cost more to ship than 1 carton @ 40lbs. Exception would be hundred weight pricing for heavier shipments when using the total weight and if the minimum charge is met
https://wwwapps.ups.com/ctc/request