I haven't seen a listing of the exact interior dimensions -- perhaps others can help you there -- but I can assure you that at 6'3" there will be plenty of room to spare. In fact, up to 6'7" or so you would be comfortable. At one test drive I attended, a 6'9" man took a drive. He fit in the car easily. Although he said he wished he had a little more room for his knees, he had enough headroom. If you're heavy as well as tall, you'll probably find that the Smart's seats are easier to get into and out of than those of many larger cars.