Would it work for Lettermail/LightPacket/Small Packet too?
Almost 100% of my shipments fall into that category. Also, everything I sell weighs between 15 and 95 grams (packaged). I only use bubble envelopes.
The "values/classes" I assign are an internal thing and I proceed as follows:
First sort criteria:
Decide if under 2cm (light packet/lettermail) or over 2cm (small packet).
Light packets/lettermail, I charge $2.95/$3.95/$5.95 for CA/US/INT.
Small packets, I charge $6.95/$9.95 for US/INT.
CA is a conundrum, as we all know, and I charge $9.95 for an expedited parcel. Sometimes I gain, sometimes I lose, but with CP's delivery guarantee and subsequent aprx. 25% refunds to me, it all washes out in a month.
Second sort criteria:
Weight: Up to 10, 25, 50, 75 grams. 10, 20, 30, 40 cents surcharge.
Third sort criteria:
Cost: I add aprx. 5% of item value.
Then, I round everything up to either 29, 39, 49, 59 cents, etc. for each extra item.
It's not an exact science but seems to really work well for me. Sometimes the combination of items puts the package into the next CP weight class and what I charge falls short of actual cost (Int'l especially) but, more often, items are added to small packets (higher weight thresholds) and it's money in my pocket.
So far, never had a light packet claim and, at the risk of getting roasted here, can smugly say that I bank $300-400 in extra profit each month on a volume of apx. 300 shipments.]:)
Even if your items are bigger/heavier, you can adapt some system for your purposes. Important is to have a clear shipping cost for every item. Personally, I hate the shipping calculators and I assume that many of our buyers don't like the extra work either.
Nothing better than to have your item and shipping costs stand out clearly. Remember, you have about 6 seconds to hook the buyer.
Also, don't worry about EXACT shipping costs. Most buyers are conditioned to some flat fee or the other these days.
Judging by the amount of overpayments I receive each week, I am not so sure how much buyers even care as long as the amount charged is perceived as reasonable.
Xena