There are 20 standard amino acids that your body uses to build proteins.

Quick Scoop

  • Short, exam-style answer:
    • 20 standard amino acids are used to make proteins in humans and most life forms.
  • Slightly more nuanced answer:
    • Roughly 500 amino acids exist in nature, but only about 20 are needed to synthesize the proteins in your body.
    • Of these 20, 9 are essential (you must get them from food), and the rest are non‑essential (your body can make them).

So when people ask “how many amino acids are there?” in a biology or biochemistry context, they almost always mean: 20 protein‑building amino acids, 9 of which are essential.