An arrow can penetrate your skull if a projectile travels fast enough. It may pierce through the bone of your head and enter the brain. It will happen if the arrow has sufficient force behind it and is fired at just the right angle to make it through your skull. A few factors can influence whether or not an arrow can penetrate the head and enter the brain. Projectile Speed If you are using a bow to shoot an arrow, you must ensure that your bow has sufficient draw weight and can adequately draw back on the bowstring. The most important is projectile speed, which determines how much force is behind the arrow. A heavier, more powerful bow will allow it to penetrate the skull at a sharper angle faster. Angle of Entry Another factor is the angle at which the arrow hits your skull. It must enter a very sharp one to pierce through your head successfully. You must fire the projectile from a considerable distance and upward trajectory so that the arrow hits your head near the top, where the bone is not as thick. Shot Placement Your shot placement also influences whether or not an arrow can penetrate the skull. It can pierce the brain if you aim the spot near the center of your forehead or the back of your neck. However, if you can hit a point closer to one of these two spots, such as your eyebrow or cheekbone, it may be possible for the arrow to pass through the skull and enter your brain. An arrow can theoretically penetrate your skull if these factors are adequately aligned. However, whether or not this is a viable method of killing someone depends on several factors, such as the person’s anatomy, ability to react in time, etc. If you are intentionally trying to kill someone with an arrow, it is a much safer choice to use a different weapon instead.