Loona pH Calculator — pH, pOH and Concentrations, Converted
pH is a logarithm wearing a friendly face, and most student errors are really logarithm errors. A converter that shows all four quantities at once makes the relationships — pH + pOH = 14, [H+] × [OH-] = 10⁻¹⁴ — impossible to miss.
Convert
pH of a solution
The pH scale 0 → 14: reds are acidic, greens neutral, blues and purples alkaline.
How to Use It
- Convert: choose what you know (pH, pOH, [H+] or [OH-]), enter the value, and read all four quantities plus an acidic/alkaline verdict.
- Solution pH: for a strong acid (HCl, HNO₃) or strong base (NaOH, KOH), enter the concentration in mol/L — the tool assumes complete dissociation, as school questions do.
- Sanity-check with the scale bar: acids live at the red end, alkalis at the purple end, 7 is neutral.
How It Works
Conversions use the defining relations at 25 °C: pH = −log₁₀[H+], pOH = −log₁₀[OH-], and pH + pOH = 14. Strong acids and bases are treated as fully dissociated, so [H+] equals the acid concentration (and [OH-] the base concentration) directly. Very dilute solutions below about 10⁻⁶ mol/L are a known edge case where water's own ions matter — school questions ignore it, and the tool follows the school convention while the formula display keeps the maths honest.
Frequently Asked Questions
Why do pH and pOH add to 14?
Because at 25 °C, [H+] × [OH-] = 10⁻¹⁴ in water, and multiplying numbers adds their logarithms. At other temperatures the constant changes slightly — another reason exam questions specify 25 °C.
Can pH be below 0 or above 14?
Yes, for very concentrated strong acids/bases (10 mol/L HCl has pH ≈ −1). The 0–14 scale is the everyday range, not a law. The converter handles out-of-range values correctly.
Does it do weak acids (ethanoic acid)?
No — weak acids need Ka and an equilibrium calculation, which is a different tool. This calculator covers conversions and strong acid/base solutions, the bulk of school pH work.