pH Calculator

pH is the standard scale chemists use to describe how acidic or basic a solution is, and it's built on a deceptively simple formula: the negative base-10 logarithm of the hydrogen ion concentration. That logarithm is exactly why pH calculations trip students up — logs aren't intuitive, and going from a concentration like 0.00001 mol/L to a clean pH value (or back the other way) requires a calculator with a log function.

Our pH calculator handles both directions instantly. Enter the hydrogen ion concentration [H⁺] in mol/L to get the pH, or enter a pH value to find the corresponding [H⁺] and [OH⁻] concentrations plus the pOH. The pH scale runs from 0 to 14: values below 7 are acidic, 7 is neutral (pure water at 25°C), and values above 7 are basic (alkaline).

Whether you're finishing a titration lab, checking water quality, or verifying a chemistry worksheet answer, this calculator gives fast, precise results without needing a scientific calculator's log button.

pH is one of the most frequently used measurements in all of chemistry and biology, appearing in every acid-base unit from middle school science through graduate biochemistry. Titration labs require you to calculate pH at multiple points along a curve, equilibrium problems ask you to find pH from a weak acid's dissociation constant (Ka), and buffer calculations depend on accurately converting between concentration and pH using the Henderson-Hasselbalch equation, which itself builds on the basic pH formula. Because pH is logarithmic, a change of just 1 pH unit represents a tenfold change in hydrogen ion concentration — a concept many students initially find counterintuitive and that calculators make concrete.

Beyond the classroom, pH measurement drives real-world decisions in medicine, agriculture, and environmental science. Human blood must stay within a narrow pH range (about 7.35–7.45) or serious medical complications occur, which is why clinical labs monitor it precisely. Farmers test soil pH to determine which crops will thrive and whether lime needs to be added to raise it. Environmental agencies like the EPA monitor the pH of rivers, lakes, and drinking water because pH outside the safe range (roughly 6.5–8.5 for drinking water) can indicate contamination or harm aquatic life. In every one of these cases, the underlying math is the same pH = -log₁₀[H⁺] formula taught in introductory chemistry.