Keyword denstity

I am wondering if my keyword density should be per post or per page. I use yoast plugin on my blogs which says your keyword should be 4.5% which some people say is too high. None of my blogs really seem to rank. So should my density be for the whole page? If its per post does that look quite spammy or keyword stuffed? And if its per page should the % still be at around 4.5 or should I lower it to 1 - 1.5%?
Any help given would be greatly appreciated

Under 1% is what I typically prefer.

4.5% is certainly stuffing.

Keep it low. Don't get caught up on actual percentage. I usually only like to use my keyword once or twice per post (sometimes more if its a long post). And to make up for that small number, I load my content with LSI keywords. Google favors this nowadays.

So I should just really use my key word a couple of times per post? Maybe 4 or 5 keywords per post over ,say,6 posts per page?

Well, I always apply 1% keyword density to my clients' orders of keyword-based articles.
If I'm going to write a 500-word article, 1% of 500 words is 5. If you'll apply, say, 4% keyword density, that means the appearance of your keyword 20 times. Nobody wants to read an article that mentions a keyword phrase sentence after sentence. I'm sure you don't want to speak to someone who mentions your full name every time he speaks, do you?

Here's my practice per article:
1. Use one main keyword. Apply 1% keyword density for the main keyword.
2. Use 3 to 5 LSI terms. Mention each term once (or twice for some, if needed).

It drastically depends on the length of the phrase. The more words the phrase has, the less times it should occur on the page. If you think about it logically, it's normal to have "vacuums" now and then, but it sure stinks like optimization if you mention "best vacuums for hardwood floors 2014" even two times in your article.

Some of the best results that I've had for the long tail keywords that I was specifically targeting were the ones where the keyword density for that particular long-tail was exactly 0%.

Keep in mind that you need to focus on the page density like url, image and so on. keep it all under 1.5-2% and you will be safe.