Overview

Calculate pH from hydrogen ion concentration ([H+]) or vice versa. Used in chemistry experiments, water quality management, food science, and environmental monitoring to assess acid-base strength.

Formula

pH = -log₁₀[H⁺]
[H⁺] = 10^(-pH)

pOH = -log₁₀[OH⁻]
pH + pOH = 14 (at 25°C)

[H⁺] × [OH⁻] = Kw = 1.0 × 10⁻¹⁴ (at 25°C)

pH < 7: acidic, pH = 7: neutral, pH > 7: basic

How to Use

1. 1Enter the hydrogen ion concentration ([H⁺]) in mol/L.
2. 2Or enter the pH value directly.
3. 3pH, pOH, [H⁺], and [OH⁻] values are calculated automatically.
4. 4Use the result to determine if the solution is acidic, neutral, or basic.

Tips

• ✔A difference of 1 pH unit means a 10-fold difference in hydrogen ion concentration.
• ✔Stomach acid has pH ~1–2, blood ~7.35–7.45, bleach ~12–13.
• ✔Pure water at 25°C has a pH of exactly 7.
• ✔As temperature changes, Kw changes, so the neutral pH shifts slightly from 7.

FAQ