This movie was made in 1980, which is before PG-13 existed. But there was no blood at all, brief language, and anything sexual was so minor that it doesn't even matter. So if there was no PG-13, maybe it should have a PG. Seriously, Indiana Jones has more blood than this. But the movie itself was okay, and it had some great scenes.

one of the best john carpenter movies ever and really violent without showing any blood

If this movie opened today, it would definitely be rated PG-13. Strangely, the PG-13 remake has more then double the violence, innuendo, and language then the older R rated version. The remake was very violent with broken glass hitting one guy in the chest, and at least four lengthy scenes where people burst into flames. The original doesn't have anything nearly that violent (except for one scene where a guy is run though with an antique-looking sword, but the scene is over pretty quickly). I should mention that the original version has more drinking then the remake. In one scene several old beer cans are found on a deserted boat, and someone makes the comment that "they were like that every night." Parents should also know that the original version of The Fog has a much scarier ending then the remake. If your family is disturbed by violent scenes in movies, you should watch the original version and skip the remake. But if you consider unhappy endings more disturbing, you should watch the remake and skip the original.