Yes, Google’s Keyword Planner tool is free to use.  But you do have to be running an active Google AdWords campaign to use it properly.
If you are not running a live campaign, then Google returns uselessly large search volume ranges for a keyword (e.g. 1,000 to 100,000 a month), rather than a single estimated number of searches a month (e.g. 7,000).
-To use Google AdWords Keyword Planner, you'll need to create a Google AdWords account.
-Then, open the Keyword Planner and click on the "Search for new keywords using a phrase, website, or category" option.
-Enter the keywords you want to research in the "Your product or service" box.
-Select the location and language you want to target.
-Then, click on the "Get ideas" button.