I will say zero! Reasoning below...
I presume you mean magic, or other species with human level intelligence (or more), etc. So that is the part I would say has a lower bound of zero. I think fantasy is about setting.
Consider science fiction: We have zero evidence of any kind that FTL is possible, we have zero evidence of other species. The Star Trek transporter is effectively magic, there is no scientific evidence that such a thing is possible; even the "quantum teleportation" reports IRL are not really teleportation in the Star Trek sense. In Star Wars, carbonite is a fantasy element, so is the Ice Planet of Hoth with its utterly laughable ecosystem (what do the animals EAT?)
Science fiction is littered with magical elements that have no scientific plausibility whatsoever, but what makes it science fiction is the setting and beliefs of the characters that their tools ARE scientific. All the crew of the Enterprise believe completely that their Warp Drive is an engineering marvel, that "warp particles" exist, that "tractor beams" have a scientific explanation and artificial gravity is easy to generate with some kind of "plate" material. That Time Travel is possible.
Most importantly, that intelligent and highly technological life (with Warp technology) has developed everywhere in the Galaxy and likely in other Galaxies too), that can speak and reason like people. How is a Ferengi different than a Troll? How is a Klingon different than an Ogre?
In The Next Generation, Q is a 100% magical god of a being, effectively immortal and capable of magic, but the characters believe Q has some scientific way of accomplishing his feats.
The same is true of fantasy. What makes it fantasy, instead of science fiction, is the setting and beliefs and attitudes of the characters. The "fantasy" elements you devise do not require magic, they can be religions, cultures, even plants, animals or ideas that did not actually exist.
It is not fantasy to think other humanoid species could exist; there is scientific evidence they did! Just 50,000 years ago Homo Sapiens lived alongside Neandertals, Denisovans, and Homo Florensis: Three distinctly different DNA types; and although we don't know what Denisovans looked like, Neandertals looked like fantasy Trolls and Homo Floresiensis were dwarfish, half our height.
I will concede that if you have something called magic in your story that cannot be anything but, then you have a Fantasy.
But to me what is fantasy is more about a setting and the knowledge of characters in the story. They may have a drink that cures illness, and believe it a magic potion, when I can devise such a drink for you in real life: It just contains a dilute antibiotic that occurs naturally (like those in bread mold). In the story the witch that brews this drink is following a recipe that is chemically sound.
In short, magic can appear to be science fiction, and science fiction can appear to be fantasy, and the real difference is in how it is presented, the setting, and what the characters believe about what they see and hear. You do not truly need any actual magic for your story to be a fantasy. But it helps!