There are a few different schools of thought when it comes to headlight height, but the general consensus is that they should be about 4 inches higher than the center of the headlight from the ground. This will ensure that they are high enough to illuminate the road ahead, but not so high that they blind oncoming traffic. Of course, your individual mileage may vary depending on the make and model of your car, so it's always best to consult your owner's manual before making any adjustments.