The overall keyword density should be 1% to 4% for article, doesn't matter if its 500 or 1000 word article. The condition is, article should be readable and shouldn't look like it's keyword stuffed. So, don't add keyword unnecessarily just to make it seo optimized, even 2% density will be ok.
When I have to freelance-copywrite I try to get my keyword density up to 4-5%. If I realise that what I'm writing looks like blatant keyword-stuffing I'll lower it down to 2-3%, but it all depends on what I'm writing about. Interesting copy about a relevant topic usually lets me get 5% without having to think about it too much.
the best way to explain this would be... ...write your keyword every 100 words... So this applies to anything ...500+ words article...
After lots of personal experience I'd say 2-3% keyword density naturally will make your content king.
Keyword is a most impotent thing in content. If you want good quality of content then 2-3% keyword density in enough.
I agree with HighTechOcean and gorrior. My clients usually do not allow me to go above 2-3%. So for a 500-words article, you can use 10-15 keywords (or that many times), but see to it that they are uniformly distributed or evenly spaced. If you put all keywords in one place or 'overstuff' your content beyond the recommended density for fast indexing - 'over-optimization' as some call it, it may cause search engine bots to reject the page. True. Make sure that keywords flow properly with the content so that it looks natural, not spun.
I've heard up to 4%. It's hard to say an exact number but in my experience it's hard enough to write a natural article with more than that anyway.
Simple keyword density is no longer working with a simple percentage. Your text has to send the important signals to the search engine, that the text itself is about "keyword topic". So, if you want to rank for "acne treatment", a simple keyword density won't help, you will have to supply all (most) related keywords. This (supplying the related keywords) is the only way to tell Google that your text is about "Keyword". So for "ance treatment", you will have to supply as well "skin", "products", "care", "clear", "time", "effective", and many more terms, that relate to "acne treatment". Proof? Sure, look how top 16 ranking sites for "acne treatment" are using the related terms: http://www.text-tools.net/analysis/2/2f320570/U0GdV17PoeTICcAT/index.html . They do not care for keyword density for "acne treamtent", they cover various topics of the theme "acne treatment".
Hi, I am unsure of the exact numbers but hope to chip in well. Range : 2%-4% It depends on the number of articles, in this case 500 words, should be close to 2.5% range. A higher number of keywords should come close to 4% and at max! Good Day, Commoner