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Hydrogen & Hydroxide Ion Calculator from pH

One pH reading determines both ions in water, because their product is fixed: K_w = [H⁺][OH⁻] = 1.0×10⁻¹⁴ at 25 °C. Enter pH and get the full ionic picture.

Hydrogen & Hydroxide Ion Calculator from pH

[H+]=10−pH,[OH−]=Kw[H+][H^+] = 10^{-pH},\quad [OH^-] = \frac{K_w}{[H^+]}

How to interpret the result

Worked check: pH 4.50 → [H⁺] = 10^(−4.50) = 3.16×10⁻⁵ M; [OH⁻] = 10^(−9.50) = 3.16×10⁻¹⁰ M. Multiply them: 1.0×10⁻¹⁴ = K_w. ✓

Assumptions

  • Pure water chemistry at 25 °C (K_w = 1.0×10⁻¹⁴)
  • No other acids or bases present