Acids are among the most important chemical substances, playing essential roles in industrial manufacturing, scientific research, medicine, and countless natural processes. While most people are familiar with common acids such as hydrochloric acid or sulfuric acid, an elite group known as superacids possesses proton-donating abilities far beyond those of conventional mineral acids. These extraordinarily powerful compounds can protonate substances that are normally considered chemically inert, making them indispensable in advanced chemistry and materials science. Measuring the strength of these acids requires specialized scales, such as the Hammett acidity function, because traditional pKa values are no longer sufficient for the strongest examples.
Here are the top 20 strongest acids in the world.
| Rank | Acid | Chemical formula | Type | Approximate acidity (H₀ or pKa) |
| 1. | Fluoroantimonic acid | HSbF₆ | Superacid | H₀ ≈ -31 |
| 2. | Fluoroarsenic acid | HAsF₆ | Superacid | H₀ ≈ -28 to -30 |
| 3. | Magic acid | FSO₃H·SbF₅ | Superacid | H₀ ≈ −23 |
| 4. | Carborane acid (H(CHB₁₁Cl₁₁)) | H(CHB₁₁Cl₁₁) | Superacid | H₀ ≈ -18 to -20 |
| 5. | Carborane acid (H(CHB₁₁F₁₁)) | H(CHB₁₁F₁₁) | Superacid | H₀ ≈ -18 |
| 6. | Perchloric acid | HClO₄ | Mineral acid | pKa ≈ -15.2 |
| 7. | Fluorosulfuric acid | HSO₃F | Superacid | H₀ ≈ -15.1 |
| 8. | Triflic acid | CF₃SO₃H | Superacid | pKa ≈ -14.7 |
| 9. | Perfluorobutanesulfonic acid | C₄F₉SO₃H | Superacid | pKa ≈ -13 to -14 |
| 10. | Bis(trifluoromethanesulfonyl)imide | HNTf₂ | Superacid | pKa ≈ -12 |
| 11. | Chlorosulfuric acid | ClSO₃H | Superacid | pKa ≈ -11 |
| 12. | Hydriodic acid | HI | Hydrohalic acid | pKa ≈ -10 |
| 13. | Hydrobromic acid | HBr | Hydrohalic acid | pKa ≈ -9 |
| 14. | Hydrochloric acid | HCl | Hydrohalic acid | pKa ≈ -6.3 |
| 15. | Sulfuric acid | H₂SO₄ | Mineral acid | pKa ≈ -3 |
| 16. | Nitric acid | HNO₃ | Mineral acid | pKa ≈ -1.4 |
| 17. | Hydrobromous acid | HBrO | Oxyacid | pKa ≈ -0.8 |
| 18. | Hydrofluoric acid | HF | Hydrohalic acid | pKa ≈ 3.2 |
| 19. | Phosphoric acid | H₃PO₄ | Mineral acid | pKa ≈ 2.15 |
| 20. | Acetic acid | CH₃COOH | Organic acid | pKa ≈ 4.76 |
