If you still have your Service and Warranty and Book, you can look there to find the length of coverage for your car—BMW’s standard factory warranty is 4 years and 50,000 miles, so you can just subtract the time from the date you bought it to find out how much is left.
Another way to keep track not only of how much warranty is left but also of service you’ve had under the warranty is to create an account for yourself at bmwusa.com and tie your VIN to it.
If all else fails, you can always call your BMW dealership and they’ll be able to look up your warranty information for you.