pH & pOH Calculator
pH & pOH Calculator
pH and pOH always add up to 14 (at 25°C), and both are directly related to the concentrations of hydrogen ions [H+] and hydroxide ions [OH-]. Enter whichever one of the four you know, and this calculator converts it to the other three, shown alongside a visual 0-14 pH scale.
pH below 7 is acidic, above 7 is basic (alkaline), and exactly 7 is neutral — the same as pure water at room temperature — but the scale itself is logarithmic, not linear, which is a detail that trips people up: each whole pH unit represents a full tenfold change in hydrogen ion concentration, so a solution at pH 3 isn't just "a bit more acidic" than pH 4, it's ten times more acidic, and a hundred times more acidic than pH 5.
- pH = -log₁₀[H+], and pOH = -log₁₀[OH-], with pH + pOH = 14 always holding at room temperature.
- pH below 7 is acidic, pH above 7 is basic (alkaline), and pH exactly 7 is neutral - like pure water.
- Each whole pH unit represents a 10x change in [H+] concentration, so pH 3 is ten times more acidic than pH 4.
How do I calculate pH from hydrogen ion concentration?
pH = -log₁₀[H+] - for example, a [H+] concentration of 1 × 10⁻³ mol/L gives a pH of exactly 3.
What is the pOH if the pH is 3?
Since pH + pOH = 14, a pH of 3 means pOH = 11.
pH & pOH Calculator
pH and pOH always add up to 14 (at 25°C), and both are directly related to the concentrations of hydrogen ions [H+] and hydroxide ions [OH-]. Enter whichever one of the four you know, and this calculator converts it to the other three, shown alongside a visual 0-14 pH scale.
pH below 7 is acidic, above 7 is basic (alkaline), and exactly 7 is neutral — the same as pure water at room temperature — but the scale itself is logarithmic, not linear, which is a detail that trips people up: each whole pH unit represents a full tenfold change in hydrogen ion concentration, so a solution at pH 3 isn't just "a bit more acidic" than pH 4, it's ten times more acidic, and a hundred times more acidic than pH 5.
- pH = -log₁₀[H+], and pOH = -log₁₀[OH-], with pH + pOH = 14 always holding at room temperature.
- pH below 7 is acidic, pH above 7 is basic (alkaline), and pH exactly 7 is neutral - like pure water.
- Each whole pH unit represents a 10x change in [H+] concentration, so pH 3 is ten times more acidic than pH 4.
How do I calculate pH from hydrogen ion concentration?
pH = -log₁₀[H+] - for example, a [H+] concentration of 1 × 10⁻³ mol/L gives a pH of exactly 3.
What is the pOH if the pH is 3?
Since pH + pOH = 14, a pH of 3 means pOH = 11.