What is pH?
The pH Calculator computes the pH (potential of hydrogen) of a solution from its hydrogen ion concentration [H⁺], and also provides pOH and hydroxide ion concentration [OH⁻]. pH is one of the most fundamental concepts in chemistry, measuring how acidic or basic a solution is on a scale of 0 to 14.
pH < 7 = Acidic (lemon juice pH 2, vinegar pH 3, coffee pH 5) pH = 7 = Neutral (pure water) pH > 7 = Basic/Alkaline (baking soda pH 9, bleach pH 13)
pH is used in chemistry labs, biology (blood pH must stay at 7.35-7.45), agriculture (soil pH affects nutrient absorption), food science (preservation), water treatment, aquariums, and swimming pools.
The pH scale is logarithmic — a pH of 3 is 10 times more acidic than pH 4, and 100 times more acidic than pH 5. This is why small pH changes can have dramatic effects.
Formula
pH = -log₁₀[H⁺] pOH = -log₁₀[OH⁻] pH + pOH = 14 (at 25°C) [H⁺] × [OH⁻] = 10⁻¹⁴ (water dissociation constant at 25°C)
Example — [H⁺] = 0.001 M: pH = -log₁₀(0.001) = -log₁₀(10⁻³) = 3 pOH = 14 - 3 = 11 [OH⁻] = 10⁻¹¹ M Nature: Acidic
Common pH values: Battery acid: 0 | Stomach acid: 1.5 | Lemon juice: 2.3 Vinegar: 2.9 | Coffee: 5 | Milk: 6.5 Pure water: 7 | Blood: 7.4 | Seawater: 8.1 Baking soda: 9.5 | Bleach: 12.5 | Drain cleaner: 14
How to use this pH Calculator?
1. Enter the hydrogen ion concentration [H⁺] in moles per liter (molarity). Example: 0.001 M = 10⁻³ M. 2. Temperature is set to 25°C (standard). At higher temperatures, the neutral pH shifts slightly below 7. 3. See pH, pOH, OH⁻ concentration, and whether the solution is acidic, neutral, or basic.