The answer to this question obviously depends on a number of factors.
1 – Creating Your Mark & Doing A Search

If you believe you’ve created a mark that is unique enough to be registered with the USPTO—ideally, you or your trademark attorney have done a comprehensive trademark search to make sure it isn’t confusingly similar to an existing trademark—then you’re ready to submit it for approval.
How long does a trademark search take? It could be a week, maybe 2. A lot of this depends on the style of your mark, whether or not you have a (competent) trademark attorney, or, if you’re doing it yourself, how much time you have on your hands to make the search.
In any case, once you believe you’ve made a mark that’s unique enough, it’s time for step 2.
2 – Filing Your Application With The USPTO

There are a number of things involved in this process, and trademark attorneys can help you cover all of your bases.
Getting all of the paperwork together and finally submitting the application is a success in itself, but you have to keep in mind that it will probably take at least 3 months before anyone at the USPTO even looks at your application.
3 – Approval & Publication

After the typical 3 month waiting period before someone at the USPTO examines your mark, they will approve or deny it.
If your mark is denied, you’re basically back to square one—recreating your mark against existing trademarks to ensure its uniqueness and likelihood of approval, and then resubmitting it.
If your mark is approved, it goes up for publication. This is a time period where people, parties, and businesses can challenge your trademark—that is to say, make claims against it and argue that it shouldn’t be registered because it’s too similar to their own or to another trademark.
The publication time period is usually one month to 45 days.
4 – Finalization

If your mark passes through the publication process unscathed, the USPTO will do some final inspections and then officially register your mark.
What You Can Realistically Expect
With so many factors at play when it comes to registering your trademark, it’s not possible to give an exact timeframe. The USPTO might deny your mark, you might not fill out or submit your information correctly, someone might convince the USPTO to deny your mark during the application period, etc. etc… (This is why having an attorney for trademark registration is so important—he or she can make sure everything is in order so you don’t experience too many setbacks.)
However, there is an average time for trademark registration that we can reasonably state: From start to finish, trademark application will probably take a minimum of 6 months, but it could take as long as 18 months to 2 years.
Don’t take our word for it—the following video is a trademark attorney being brutally honest about the trademark process and how much time you’re actually looking at.
Long story short: Successful trademark registration takes patience and the help of an experienced trademark attorney.