is first class and parcel post two different things?? I mailed 5 packages on saturday. I had two books so of course they were marked media mail but the rest I said whatever is the cheapest. Well I could swear that first class and parcel post are two different classes of mail and that parcel post was always cheaper even though it takes longer. Well this guy just sent everything other than the books media mail. I was sooo not happy that I spent so much on two packages that were not urgent. One was a cd so of course that would go first class. So do I need to specify like I do with the books so I don't get over charged again?

Yes, they are two different things.  Here's what the USPS website has to say...

Use Parcel Post® when value is most important. Small and large packages, thick envelopes and tubes containing gifts and merchandise can be sent using Parcel Post. Delivery to every address in the United States-including PO Boxes and military addresses. Saturday and residential deliveries at no extra cost Parcel Post packages can weigh up to 70 pounds and measure up to 130 inches in combined length and distance around the thickest part For discount rates see Parcel Select. Rates are based on weight, distance, and shape. A surcharge applies to certain items including packages weighing over 35 pounds (25 pounds for books and printed matter) and certain shapes (e.g. tubes, rolls, and large packages).

Here are some prices for the three different types of mail you mention:

Priority Mail (varies by zone, I'll give worst case pricing):

under 1 pound $4.60

1-2 pounds $7.50

2-3 pounds $10.55

3-4 pounds $13.45

4-5 pounds $15.85

Media Mail (no zones):

under 1 pound $2.13

1-2 pounds $2.47

2-3 pounds $2.81

3-4 pounds $3.15

4-5 pounds $3.49

Parcel Post (varies by zone AND whether or not is is "machinable"...I'll give top rate in each of these):

under 1 pound $3.96/6.83

1-2 pounds $4.72/7.59

2-3 pounds $5.46/8.33

3-4 pounds $6.13/9.00

4-5 pounds $6.76/9.63

I think they are the same, parcel post is a package rate on first class mail. When you pull up a list of shipping rates on a package you get (cheapest to most expensive):

Media Mail

Parcel Post

Priority

Express

eta (and then reformat a billion times): Anything over 13 oz apparently isn't techinically First Class, you cannot send it First Class, you either go to Parcel Post or up to Priority for none MM.

OK so that formating doesn't work. " First-Class Mail® is used for personal and business correspondence. It includes postcards, letters, large envelopes, small packages, and any mailable item weighing 13 ounces or less. ..."

No, Parcel is not always cheaper than First Class Package rate. In fact, if a non-media item qualifies for First Class, then take it. The rules I follow are listed below. Of course, they may change when the new rates take effect next week, but they will still be pretty close.

I LOVE my postal workers, but sometimes they need a little help, so I never let them pick the rates for me. here are the rules of thumb that  I follow:

• under 7 oz., First Class Package is your best rate, including books
• 7 - 13 oz. First Class Package is your best rate for everything except that which qualifies for Media.
• over 13 oz. you don't even get offered First Class Package, you just get Parcel Post or Priority, which are sometimes only pennies apart, anyways.

Corollaries:

• If you sent something Parcel that could have gone First Class Package, you overpaid.
• If you sent something under 7 oz. via Media, you overpaid.
• Otherwise, you got the best rates.

(note to above rules: 7 oz. First class is only 2 cents more than Media Rate, so I usually choose First Class anyways)

1st class is 13 ounces or less. There are 3 categories for 1st class, letter, large envelope and parcel. Each category starts at a different rate for the first ounce.

If you sent something 1st class parcel, you paid the lowest rate for that item. Parcel post is cheaper when the package weighs more than 13 ounces. Often at lower weights the difference is a dime (or the same price if you use the retail delivery confirmation). Ask the difference if you are not sure what to choose.

Parcel post means it will go by truck. The further the destination, the longer it may take. Even being close by can take a long time because of  where it is sorted. Media mail travels the same.

Most of the prices will change on Monday, May 12th. There will be a discount for priority mail and express when you use online postage. I have not figured out all the new prices and options starting next week. I will be learning all this wonderful information over the next week or so. Post or PM and I will research options if anyone wants help.

Sorry...I had a brain fart and confused Priority with First Class.  As others have mentioned, First Class only goes up to 13 ounces and is sometimes the cheaper option.  The price info I gave is a comparison of Priority/Media/Parcel.