Old question now, but interesting none the less and currently marked as unanswered. As tomcraig86 says there is much more to it than relying on the KD score, but I tend to go by the rough guide of :
- Sub 30 - pretty easy.
- 30 - 35 fairly easy with good on page and some quality anchored links.
- 35 - 40 - starting to take a bit more effort, air tight on-site SEO required as well as good link profile.
- 40 - 50 domain authority counts much more, without it will take longer to rank although I have done this with minimal off-site efforts before.
- 50+ All about resources. Onsite SEO needs to be totally nailed, including internal linking/ topic modelling etc. a strong & diverse link profile with good social signals and ... time.
This is just from my experience of ranking for keywords in conjunction with output from this awesome tool. Been doing SEO for some time, but only using the keyword difficulty tool for about 12 months.
