Buffer pH (Henderson–Hasselbalch) calculator with steps
Document every Henderson–Hasselbalch step: convert HA/A⁻ amounts to moles, compute pH, design buffer recipes for a target pH, and simulate strong acid/base additions with buffer capacity.
Use it as a classroom companion or lab prep tool: see molar conversions, ratio r, and the assumptions behind the H–H approximation alongside a shareable How it’s calculated log.
Notes & assumptions
The Henderson–Hasselbalch approximation assumes a buffer where both HA and A⁻ remain present. Extremely small ratios (r < 0.01) or very large ratios (r > 100) break that assumption, as do pH values near the extremes of water auto-ionisation. Watch for warnings and switch to a full equilibrium solver if one component is depleted.
β is computed as 2.303·CT·(Ka[H⁺])/(Ka+[H⁺])², with an optional water contribution [H⁺]+Kw/[H⁺]. Set CT to the buffer’s total analytical concentration for the best estimate.
Related calculators
How it's calculated
- Uses Henderson–Hasselbalch: pH = pKa + log10([A−]/[HA]).
- Assumes dilute solutions; units and ionic strength simplified.
- Share URL preserves inputs.