pH Calculator
Enter any one of pH, pOH, [H+] or [OH-] and instantly get the other three plus an acid/base classification.
Input type
Acidic
- 1
pOH = 14 − pH
14 − 3 = 11 - 2
pH
3
How does this calculator work?
The pH calculator converts between pH, pOH, [H+] and [OH-]. Enter any one value: it computes pH = -log10([H+]), uses pOH = 14 - pH (Kw = 1e-14 at 25 C), and reports hydrogen and hydroxide concentrations plus an acidic, neutral, or basic classification of your solution.
Formula
How this is calculated
Select which quantity you know with the input type dropdown, then type its value. If you give a hydrogen ion concentration [H+] in mol/L, the calculator computes pH = -log10([H+]). Because the ion product of water Kw = [H+][OH-] = 1e-14 at 25 C, the corresponding pOH is simply 14 - pH, and the hydroxide concentration is [OH-] = 10^(-pOH).
If instead you supply pH directly, the chain runs in reverse: [H+] = 10^(-pH), pOH = 14 - pH, and [OH-] = 10^(-pOH). The pOH and [OH-] modes work the same way, first converting your value to pH before deriving everything else. Concentrations must be positive (logarithms of zero or negative numbers are undefined), so those inputs are rejected.
The result is classified as acidic when pH is below 7, basic (alkaline) when above 7, and neutral at 7. Note the relationship pH + pOH = 14 holds only at 25 C; at other temperatures Kw and the neutral point shift slightly.
Frequently asked questions
pH equals the negative base-10 logarithm of the hydrogen ion concentration in mol/L: pH = -log10([H+]). For example, [H+] = 1e-3 mol/L gives pH 3.
At 25 C the water ion product gives pH + pOH = 14, so pOH = 14 - pH. This lets you find hydroxide concentration from pH and vice versa.
A solution with pH below 7 is acidic, exactly 7 is neutral, and above 7 is basic. The scale typically runs from 0 to 14.
Also known as
TG we-Calculate Editorial Team. (2026). pH Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/ph-calculator
TG we-Calculate Editorial Team. "pH Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/ph-calculator.
TG we-Calculate Editorial Team, "pH Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/ph-calculator
@misc{wecalculate_ph_calculator, title = {pH Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/ph-calculator}}, year = {2026}, note = {TG we-Calculate} }
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