I had been preparing for this change for a while. So when it actually happened I was prepared. So I went to the USPS site to see if I could calculate shipping for my Etsy shop. I have a cheat sheet that I have created to help me with the new shipping prices in my shop. I weighed each of my items in a bubbled envelope and input the weight in the Postage Price Calculator. I use the international places that I ship to the most to get shipping price quotes.
I tried this with a package that I had to ship international and the price that it showed on the Postage Price Calculator was the exact same when I went to ship at the post office. So I would say enter a few of the places that you commonly ship to in order to get a quote on how much it will be. This way you will know how much it will exactly cost you to ship an item.
If you thinking about cutting out international shipping in your shop, I would think it over first. There are other ways that you can cut back so that you can still service international buyers.
You can find the USPS Postage Price Calculator HERE Or you can go and download the app from the Apple market and use the calculator there.