Ka to pKa
Type a value in Ka to get it in pKa instantly.
-0.6776pKa
That's 12× as weak as the hydronium ion, while formic acid is 26,767× weaker. That is a strong acid: essentially fully dissociated in water.
Convert the other way: pKa to Ka
What it means
How strong is that acid?
Values are for water at 25 °C. pKa shifts with solvent and temperature, and in a protein an ordinary side chain can move several units.
The math
How to convert Ka to pKa
pKa is a logarithm: pKa = −log₁₀(Ka), and back again Ka = 10^(−pKa). In water at 25 °C, pKa + pKb = 14, and the free energy is ΔG° = 5.708 × pKa kJ/mol.
Example: 4.76 Ka = -0.677607 pKa.
Every unit
Your acid strength in every unit
Tables
Ka to pKa conversion table
| Ka | pKa |
|---|---|
| 1×10⁻¹⁶ Ka | 16 pKa |
| 1×10⁻¹⁴ Ka | 14 pKa |
| 5.01×10⁻¹¹ Ka | 10.3002 pKa |
| 5.62×10⁻¹⁰ Ka | 9.25026 pKa |
| 6.31×10⁻⁸ Ka | 7.19997 pKa |
| 4.47×10⁻⁷ Ka | 6.34969 pKa |
| 1.74×10⁻⁵ Ka | 4.75945 pKa |
| 0.000178 Ka | 3.74958 pKa |
| 0.01 Ka | 2 pKa |
| 1 Ka | 0 pKa |
| 1,000 Ka | -3 pKa |
| 10,000,000 Ka | -7 pKa |
| 1×10¹⁰ Ka | -10 pKa |
pKa to Ka conversion table
| pKa | Ka |
|---|---|
| -10 pKa | 1×10¹⁰ Ka |
| -7 pKa | 10,000,000 Ka |
| -3 pKa | 1,000 Ka |
| 0 pKa | 1 Ka |
| 2 pKa | 0.01 Ka |
| 3.75 pKa | 0.000177828 Ka |
| 4.76 pKa | 1.738×10⁻⁵ Ka |
| 6.35 pKa | 4.467×10⁻⁷ Ka |
| 7.2 pKa | 6.31×10⁻⁸ Ka |
| 9.25 pKa | 5.623×10⁻¹⁰ Ka |
| 10.3 pKa | 5.012×10⁻¹¹ Ka |
| 14 pKa | 1×10⁻¹⁴ Ka |
| 16 pKa | 1×10⁻¹⁶ Ka |
Quick answers
Quick answers
- How many pKa is 1 Ka?
- 1 Ka is 0 pKa.
- How many pKa is 10 Ka?
- 10 Ka is -1 pKa.
- How many pKa is 4.76 Ka?
- 4.76 Ka is -0.677607 pKa.
The units
About these units
Ka (Ka)
The dissociation constant itself, in moles per liter.
pKa (pKa)
The negative logarithm of the dissociation constant. Lower means stronger.
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