Using Google’s Traffic Estimator tool is a good way to get an idea of how much a new campaign is likely to spend once it is launched. Nobody expects this tool to be perfectly accurate, I’m sure, but I always wondered just how accurate it is so I did a little test.

To start, I ran a Placement/Keyword report for all keywords in one of my higher volume campaigns and calculated the average keyword metrics over a 30 day period (CPC, clicks and cost) for 16 unique keywords. Then, I plugged these keywords into the Traffic Estimator Tool so I could compare the estimates to actual keyword performance averages.

For every keyword, the Traffic Estimator tool provides lower and upper estimates for daily clicks, cost and CPCs, assuming the keywords are bid to appear in positions 1-3 (actual average position for my keywords was 3.3). Here is what I found:

Google Click Estimates:

Over a 30 day period, the keywords in my list averaged 7.08 clicks per day. Google lower estimate predicted 6.38 clicks daily, or 0.7 clicks under actual average daily clicks. Google upper estimate predicted 8.5 clicks daily or 1.42 clicks over the actual 30 day average. Pretty close!

Google CPC Estimates:

Over a 30 day period, the keywords in my list averaged a daily CPC of $0.54. Google lower estimate predicted an average CPC of $0.93, or $0.39 over the actual average daily CPC. Google upper estimate predicted $1.53 or $0.99 over the actual day average CPC. Not bad.

Google Daily Cost Estimates:

Over a 30 day period, the keywords in my list generated an estimated total cost of $78.84 daily (based on their average daily cost). Google lower estimate predicted a total cost of $162 daily, or $83.56 over actually daily cost averages. Google upper estimates predicted a total cost of $250 daily, or $176.51 over actually daily cost averages. Not so good.

Google Monthly Cost Estimates:

Multiplying the actual average daily cost per keyword by 30, it is estimated that these keywords have spent a total of $2,353.32 for the month. Multiplying Google lower daily cost estimates by 30 predicts a total monthly cost of $4,860 or $2,506.68 over actual total monthly cost. Multiplying Google upper daily cost estimates by 30 predicts a total monthly cost of $7,500 or $5,146 over actual total monthly cost. Yikes!

Could daily budget caps have prevented my campaign from reaching the cost estimates Google predicted? It’s possible. This campaign in particular spent an average of 55% under the daily budget cap over the same 30 day period. But then again, bid optimization and general tweaking could have played a role as well. Perhaps if I had let the campaign run wild with no supervision Google’s predictions may have been more accurate.

Overall, it looks like the lower estimates tend to be more accurate than the upper estimates, at least for this particular list of keywords. Daily click volume and average CPC estimates are pretty accurate for the time range I sampled. Daily cost estimates are not quite as accurate. So, perhaps there is room for improvement in the accuracy of Google’s Traffic Estimator tool but it is still a great place to start when building an account or even a single campaign to get a ballpark idea of how much the campaign might spend.