https://www.canadapost.ca/cpotools/apps/far/business/findARate?execution=e1s1
Play with the dimensions and weights.
If you are shipping something that can be sent LetterPost/LightPacket, Flat Rate Shipping is fine*.
In fact, you could even take a deep breath and make those items Free Shipping.
Free Shipping just means adding the cost of shipping and packaging to your asking price.
Buyers, especially the 52% using mobiles, love it.
If your item must go Package Rates, stay on dotCA and use Calculated Shipping.
Package rates are based not only on weight and dimensions but on distance.
Here are two or three postal codes: K1A 0A6, V8R 5G8, A1C 5S7.
Here are a couple of zipcodes: 90210 , 37188, 32830.
Notice how the Canadian rate can double from coast to coast? The US one is more stable.
Use METRIC measurements. Canada Post went metric in 1974, and all other systems are guesswork.
Do NOT consider selling internationally until you have at least 10 DSRs and know what DSRs are.
You don't have to know anything about the import fees for other countries. That is the buyer's responsibility.
At one point eBay was encouraging sellers to add this boilerplate to their listings for international customers.
Import duties, taxes and charges are not included in the item price or shipping charges. These charges are the buyer's responsibility. Please check with your country's customs office to determine what these additional costs will be prior to bidding/buying.
*You may also want to list those items on dotCOM rather than here, but that is a different discussion.
