I spent 6-8 hours in Pompeii and 4-5 hours in Herculaneum. If you chop down you can see Pompeii in 2-4 hours as well, but then you would miss out the immersion

I spent 6-8 hours in Pompeii and 4-5 hours in Herculaneum. If you chop down you can see Pompeii in 2-4 hours as well, but then you would miss out the immersion in ancient culture. So I wouldn't recommend visiting both at the same day.