Ammon Johns: There is no specific word-count that Google want, desire, recognize or reward any better than any other. Google is as happy to index and rank content with no word (check out Google image search, or Youtube videos Google include in the SERP), an infographic, or a scholarly article of some 30, 000 words. They are all the same to Google, just content to attempt to understand their relevance to users for.
On product pages, the right amount (and nature) of words is whatever gets the best conversion rates. There`s no point getting twice as many visits at the cost of only converting half as many of them, as that is no end gain in income. Always, on product pages, focus on selling the product to those who already land on the page, however they got there.
Use other pages to drive additional qualified leads to your product page, knowing it has the best possible chance of converting all who visit.
For content pages, again, decide what your goal is with people first. If you are building a page that has the sole or primary purpose of ranking, then it needs to be something people will naturally want to link to, talk about, pass on to others. The right number and nature of words will again be what you test and prove to do that best.
Zemayada Ranger: Ammon Johns I don`t think he was asking about some unbreakable law prescribed by Google. He`s just looking for a guideline to get started. 300 words is best limit to be set for a concise description of whatever the product we`re talking about.
Ammon Johns: Zemayada Ranger why 300 when Google don`t care if it is one word or 1 million?
Do you know who made up the idea of word counts? Cheap outsource article writers, so they could standardize a product.
Heck, even in the pre-Google years when many search engines only used on-page, and people believed in keyword count and keyword density, they believed every engine had a different `taste` whether for long or short, and the long even then was 1500 words or more.
Please, do tell me why you think 300 words is some magic amount that will suit every product from simple pairs of socks to complicated solar energy systems.
Zemayada Ranger: `A guideline to get the project started.` It`s written right there the first time I replied. It`s just an ecommerce page, you don`t need to go overboard with 1500, incessantly rambling.
Ammon Johns: Zemayada Ranger the trouble is we don`t know the product. You`ll struggle to write 300 meaningful or useful words that won`t put customers off by looking like keyword stuffing for a generic commodity product, such as plain old regular socks. Not unless you are going to list the names of the sheep used for the wool.
But 300 words to sell a house, a yacht, or complex software/hardware systems would be ridiculously little, especially where the buyer may not be the sole user (e.g. B2B sales, where the exec doing the research is looking at options he`ll then have to present in a meeting with various stakeholders, the users are not the buyers because there is a purchasing dept, and the users are also probably not the tech guys who have to okay it).
How many (well written) words should we have on our product pages and pages? We have an e-commerce 
