TL;DR – SEMrush was the only tool out of the five that matched with Google’s very own search volume data for all of the 80 keywords. Ubersuggest was the runner up with only 1 mismatch. Does this make these two tools superior to the other three? Possibly, but not definitively. Keep reading for more context and insights.
Ever wondered where does your favorite keyword research tool pull the search volume data from and, even more importantly, can you trust it?
I decided to do an experiment and put five popular keyword research tools to test.
Firstly, I came up with 80 random keywords divided into 4 brackets (20 keywords per bracket):
- One-word keywords
- Two-word keywords
- Three-word keywords
- Five-word keywords
The reason for these brackets is I wanted to cover both short-tail and long-tail keywords.
I also wanted to include keywords with millions of monthly searches and those with only a few thousand searches per month.
The idea was to pull the data from five popular keyword research tools and compare it with Google Keyword Planner’s search volume data.
You will notice that Google Keyword Planner only provides search volume in brackets (e.g. 0-10, 10-100, 100-1k, 1k-10k, etc.) and doesn’t give you an “exact” estimate which slightly dilutes the findings of this comparison.
Still, useful insights can be drawn here and I’m taking Google’s data as a point of reference nonetheless because it makes the most sense.
Important: All of the search volume figures in this experiment are localized to the United States only. In other words, they’re not global search volume figures.
How is search volume calculated?
Different tools calculate search volume differently.
Google Keyword Planner shows the average monthly search figures for your keyword and its close variants.
KWFinder uses Google’s data among other sources but it shows separate search volume for each keyword individually and does not add any search volume data from close variants.
Ahrefs uses the anonymized data from various browser apps and plugins (aka clickstream data) combined with the Google Keyword Planner data to create models that crank out their search volume estimates.
SEMrush also uses the clickstream data in tandem with machine learning to calculate the search volume for their tool.
Keyword Surfer and Ubersuggest do not disclose their search volume calculation methods but it’s safe to assume they’re probably doing similar things to what the other three tools are doing.
Without further ado, let’s check out the experiment results!
Experiment Results
Note:Red numbers mean there was a mismatch in search volume figures between the Google Keyword Planner and the respective tool.
One-Word Keywords
As you can see, Ahrefs search volume figures mismatched with those of Google Keyword Planner 6 out of 20 times in this batch of keywords.
Keyword Surfer’s data mismatched once.
Note: For some reason, all of the tools severely overestimate the search volume for the very first keyword which is “youtube.” Additionally, for reasons unknown, Google Keyword Planner did not want to show any estimate for the keyword “computer.”
Two-Word Keywords
Again, Ahrefs mismatched more often than others, 5 times.
Keyword Surfer mismatched 3 times.
KWFinder mismatched twice and Ubersuggest mismatched once.
Note: “Computer repair” keyword returned the oddest results. First, Google Keyword Finder refused to show any estimate for it, and then Keyword Surfer and Ubersuggest returned search volume of zero for that keyword, which can’t be correct. People do search for “computer repair” quite often. The reasons for these discrepancies are unknown.
Three-Word Keywords
Ahrefs mismatched 5 times.
Keyword Surfer mismatched twice.
KWFinder mismatched once.
A couple of very odd results were uncovered in this batch of keywords.
Keyword Surfer returned the search volume of 0 for the “download youtube videos” keyword and KWFinder returned the search volume of 10 for the “college football scores” keyword.
Both results are severely wrong since the search volume for both of these keywords is measured in millions.
Five-Word Keywords
Ahrefs mismatched 8 times.
Keyword Surfer and KWFinder mismatched twice.
The largest mismatched in this final batch comes from Keyword Surfer that has returned the search volume of 0 for the “legend quest masters of myth” keyword.
Other tools show that this keyword indeed does have some search volume behind it.
Key takeaways and statistics
Ahrefs mismatched with Google Keyword Planner for 24 out of 80 keywords or 30% of the time.
Keyword Surfer mismatched 8 different times or 10% of the time.
KWFinder mismatched 5 different times or 6.25% of the time.
Ubersuggest only mismatched once which is 1.25% of the time.
SEMrush did not have any mismatches and was within margins of the Google Keyword Planner for all 80 keywords.
Ahrefs was the tool that regularly returned the lowest search volume estimates out of all of the five tools – 39 out of 80 times, or 48.75%.
Ubersuggest only had a single mismatch, but it was quite a blunder.
It returned 0 search volume for the “computer repair” keyword.
Keyword Surfer made the exact same blunder.
The saving grace, in this case, might lay in the fact that Google Keyword Planner also refused to return any estimates for this keyword which indicates that, for some reason, many tools are having problems with this keyword.
Two similar blunders that are inexcusable belong to Keyword Surfer (again) and KWFinder that returned 0 and 10 search volume for the “download youtube videos” and “college football scores” respectively.
Both of these keywords have hundreds of thousands (if not millions) of searches per month.
Quite a few times, there were huge discrepancies between values shown by different tools. Here are a few examples:
Ahrefs returned 6-8X less search volume than other tools for the keyword “coffee.”
KWFinder returned anywhere from 24X to the staggering 238X less search volume than other tools for the keyword “sky scanner.”
Ahrefs returned about 4X lower search volume numbers than other tools for the keyword “cooking a turkey.”
KWFinder returned anywhere from 5.5X to a whopping 21X lower search volume number than other tools for the “best youtube to mp3 converter” keyword.
Final Verdict – which tool is the best?
I give the title to SEMrush, the tool that was consistently within the margins of Google’s reported search volume data.
Ubersuggest comes in second place with only 1 mismatch.
Ahrefs had the most mismatches by a mile.
I think Ahrefs is a great tool and should not be discounted by any stretch of the imagination, however.
If you’re strictly looking for a search volume tool, Keyword Surfer is probably the best option simply because it’s completely free and can be downloaded as a Google Chrome extension on their official page.
It’s important to note that you can also use Google Keyword Planner for free if you don’t mind the volume brackets instead of more precise estimates offered by other tools.
Conclusion
This experiment demonstrates that you shouldn’t always take the search volume estimates for granted.
Various tools can return wildly different results, sometimes even dead wrong results.
Of course, search volume is not the be-all and end-all thing to take into account when performing keyword research but keep in mind the possibility that your tool could be misguiding you.
For the most important tasks like picking a niche, try using multiple tools before committing to a decision.
Better safe than sorry!
I love to read your research result Tom. I was worried about Ubersuggest because I have paid the lifetime plan. However, your research result convinced me. Thanks so much.
Glad you found the article helpful, Aliv!