Hi there,
I would suggest you specifically look at competitive intelligence tools like compete.com or semrush as they can provide somewhat accurate estimates.
But there are a lot of online tools and services that provide traffic volume estimations for keywords. They differ in many aspects – different solutions have different interfaces with different additional options available. They also use different data sources. Therefore, the best option would be to check your keywords with several solutions and compare the results. If you have no time for that – you should select the most reliable source for your estimates and stick to it.
First of all, these estimates do not take into account click distribution between different TOP positions. Even if you are ranked TOP 1 for some particular keywords, you won’t gather 100% of the traffic. Some part of the traffic will go to Google Local Business. And one more thing that cannot be predicted in advance: any keyword traffic estimator gives data about how much time a particular keyword was entered into the search field, but it cannot tell between real users and automated seo tools that check positions of a particular website for a particular keyword.
Hope it helps!