pH Calculator
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pH Result
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024678101214
How to Use the pH Calculator
Select the calculation mode using the tabs at the top of the tool, enter the required values and click Calculate pH. The result includes a visual pH scale indicator, pOH, H⁺ and OH⁻ concentrations, and an acid/base classification.
Four Calculation Modes
From [H⁺] Concentration
Enter the molar concentration of H⁺ ions. pH = −log[H⁺]. Most direct method for strong acids and known concentrations.
From pOH
Enter pOH to find pH. At 25°C: pH + pOH = 14. Used when working from OH⁻ concentration or base solutions.
Weak Acid (Ka method)
Enter Ka and concentration of weak acid. pH = ½(pKa − log C). Accurate for monoprotic weak acids where Ka is known.
Buffer — Henderson–Hasselbalch
Enter pKa and the ratio [A⁻]/[HA] or individual concentrations. pH = pKa + log([A⁻]/[HA]). Standard for buffer systems.
Key Formulas
pH = −log[H⁺] | pOH = −log[OH⁻] | pH + pOH = 14
Weak acid: pH = ½(pKa − log C) | Buffer: pH = pKa + log([A⁻]/[HA])
Weak acid: pH = ½(pKa − log C) | Buffer: pH = pKa + log([A⁻]/[HA])
About pH in Biotechnology
pH is one of the most critical parameters in biological and chemical laboratory work. Enzyme activity, protein stability, DNA integrity, cell viability and reaction rates are all tightly pH-dependent. Even a 0.1 unit change in pH can significantly alter experimental outcomes.
Common pH Reference Values
Physiological pH: 7.4
Human blood and most cell culture media are maintained at pH 7.4. PBS and HEPES buffers are commonly used to achieve this.
DNA Extraction: pH 8.0
TE buffer (10 mM Tris-HCl, 1 mM EDTA) at pH 8.0 is the standard storage buffer for DNA to prevent degradation.
SDS-PAGE Running Buffer: pH 8.3
Tris-glycine buffer at pH 8.3 is used in standard SDS-PAGE electrophoresis for protein separation.
Agarose Gel (TAE): pH 8.5
TAE buffer (Tris-acetate-EDTA) at pH 8.5 is used for DNA agarose gel electrophoresis and DNA recovery.
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