Why are vampires usually related to crosses?

The answers below pretty decently cover the question; traditionally, vampires are considered evil and unholy creatures, and are repelled by the sight of a holy symbol. read more

Thus, crosses stop vampires. I’m sure that some historians or someone with a degree in folklore could be more specific for you. But, I’m willing to bet that the whole cross = holy and vampire = undead = unholy dichotomy is the answer. read more

The real Human Vampires aren't repelled by crosses. Most vampires actually believe in Jesus Christ as our Savior, and are normal human beings that just happen to have some unusual abilities like those of a medium. Real Vampires are not possessed like one would believe, they have a reincarnated spirit as a soul. read more

It depends on the mythos. In Vampire: The Masquerade, vampires are not repelled by crosses unless the person using the cross has True Faith. In Anne Rice's Vampire Chronicles, those vampires are not affected by crosses. For people who identify as vampires (whether psychic or otherwise), crosses generally do not repel them as they are just people. read more

Before Christianity, methods of repelling vampires included garlic, hawthorn branches, rowan trees (later used to make crosses), scattering of seeds, fire, decapitation with a gravedigger’s spade, salt (associated with preservation and purity), iron, bells, a rooster’s crow, peppermint, running water, and burying a suspected vampire at a crossroads. read more