Chemistry Calculators
pKa Calculator
Find pKa from pH with conjugate base/weak acid concentrations, or directly from Ka.
Use Henderson-Hasselbalch to compute pKa from pH: pKa = pH - log10([A-]/[HA]).
You can also compute pKa from acid dissociation constant with pKa = -log10(Ka).
pKa from pH
pH
Conjugate base concentration
M
Weak acid concentration
M
pKa
pKa from Ka
Ka
pKa
pKa and pH - How to calculate pKa from pH?
Henderson-Hasselbalch equation
Use this relation to calculate pKa from pH and concentration ratio:
pH = pKₐ + log₁₀([A⁻]/[HA])
- If [HA] = [A⁻], then pH = pKₐ.
- If [HA] > [A⁻], then pH < pKₐ.
- If [HA] < [A⁻], then pH > pKₐ.
pKa and Ka
pKₐ = -log₁₀(Kₐ)