I deal with over 20,000 grocery items, mostly US manufactured, and the
most accurate way of identifying a product, to determine if the price
quoted is acceptable, is to make sure that we compare "apples to
apples" (in other words to make sure we are getting quoted the same
pack, size, count, unit, quantity, etc.).

Is there a web page, preferably free, where you can search for a UPC
Code by entering as much info as you know about the product itself?
IE: brand name, manufacturer, pack, size, and so forth.

Hi lrojas,

The following is what you are looking for but it's possible you won't
be able to find all of your products. When you test it out, don't type
in too much information by narrowing your search too fine, it's better
to return a short list to look at.

UPC Database: Search by Description
"Enter one or more words or parts of words to search for in the
product descriptions. A match will occur when all of the words that
you enter occur in a product description."
http://www.upcdatabase.com/

Another option would be to download and then search the UPC Database:
http://www.upcdatabase.com/

For a more complete list and full product detail, you can purchase a
full product database for food only from Greg London:

Electronic Product Catalog
These "Catalogs" contain:
BASIC product information - such as U.P.C., Manufacturer, Brand, Description, etc.
for various CATEGORIES of items - such as Food, Health & Beauty, Spirits, etc.
and optionally, FULL data elements, such as:
NUTRITION FACTS - Total Fat, Fat UOM, % Daily Value, etc.
INGREDIENTS - (for Fritos Corn Chips) Corn, Corn Oil, Salt, etc.
SHELF MANAGEMENT - Product Dimensions, Case U.P.C., etc.
ADDITIONAL DATA - Endorsements, Allergy Information, Warnings, etc.
Product images are also available.
My current "flagship" products include these Electronic Product Catalogs:
Food (Packaged Goods, Perishable, and Non Perishable)
Should you wish further information, Catalog Pricing, or Data Samples,
please contact me at 469-366-4278, or via E-Mail.
http://www.glondon.com/upcdatabase.html

Additional Links of Interest:

BarCode 1
Universal Product Code (UPC)
and EAN Article Numbering Code (EAN) Page
http://www.adams1.com/pub/russadam/upccode.html

UPC Lookup:
http://www.schworak.com/upc/

I hope this helps. If you have any questions, please post a
clarification request *before* closing/rating my answer and I'll be
happy to reply.

Thank you,
hummer

Google Search Terms Used: UPC codes