The answer is: nowhere, at least to find an accurate number. There has been some much needed coverage recently in the SEO world about the Google AdWords tool vs. Google’s Search-Based Keyword Tool (SKTool). To get some history, check out posts on Smackdown and David Naylor.
The various keyword tools do provide some interesting information about trending and potentially relative search volume but after looking through actual analytics, I don’t even see a trend in the discrepancies between various tools. The following is an actual example. I’m choosing not to disclose the actual keywords.
Keyword #1 – General commercial category. Something like “Fishing Net”
- SK Tool – 2800 monthly searches
- AdWords Tool – 90,500 EXACT match global monthly searches
- Ranking – #1
- Last 30 Days traffic via Google Analytics – 1,110
- SKTool CTR – 40% (reasonable)
- Adowrds Tool CTR – 1.2% (ouch)
- The SERPS for this query include Overstock at #2, Wikipedia at #3, Image results and full PPC results
So overall, this query isn’t too off. 40% CTR for the #1 spot under these conditions is great.
Keyword #2 – General commercial category. Plural of Keyword #1
- SK Tool – 190 monthly searches
- AdWords Tool – 74,000 EXACT match global monthly searches
- Ranking – #2
- Last 30 Days traffic via Google Analytics – 1,646
- SKTool CTR – 866% (in the #2 spot)
- Adowrds Tool CTR – 2.2%
- The SERPS for this query include Overstock at #1, Image results and full PPC results
As you can see, the SKTool for this query is extremely misleading as I receive more traffic for the keyword than the tool says exists. I appreciate that it is misleading on the lower side as it may scare potential competitors away but it is off, nonetheless.
Another method to estimate search volume would be to compare 2 keywords in Google trends. You should use a keyword that you are very familiar with as a baseline to the keyword you are researching and see how it stacks up. Similar to the tools above, I’m not 100% confident that this is accurate either.
In the image below, the red line represents Keyword #2 and the blue line is Keyword #1. If you recall, I currently get more traffic from Keyword #2 (in the 2nd position) than I do from Keyword #1 (in the 1st position).
To summarize, you shouldn’t fully rely on any Google Keyword tool at this time for accurate keyword estimate. The SKTool is probably the closest but don’t be surprised if it over or underestimates search volume. Use various tools to compare and look for trends and opportunities. In the end, it’s a little bit of a gamble but isn’t that separates the amateurs from the pro’s?