pH Calculator
pH from hydrogen ion concentration, or the reverse.
Enter your values
Enter the hydrogen ion concentration [h+] in mol/L.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- pH
- 4
- pOH
- 10
- Classification
- Acidic
Quick answer
pH = -log10[H+].
pH = -log10[H+]
At a glance
| What it does | pH from hydrogen ion concentration, or the reverse. |
|---|---|
| Category | Science |
| Inputs needed | Hydrogen ion concentration [H+] |
| Main output | pH |
| Formula | pH = -log10[H+] |
| Cost | Free — no sign-up, no download |
How to use the pH Calculator
- 1Enter the hydrogen ion concentration [H+] in mol/L.
- 2The calculator applies the negative log10 to find pH.
- 3Read the pOH and whether the solution is acidic, neutral or basic.
Inputs explained
- Hydrogen ion concentration [H+](mol/L)
- Enter the hydrogen ion concentration [h+] in mol/L.
Worked example
Using the values the calculator loads with:
Inputs
- Hydrogen ion concentration [H+]0.0001 mol/L
Results
- pH4
- pOH10
- ClassificationAcidic
Frequently asked questions
What is a neutral pH?
Pure water at 25°C has a pH of 7, meaning [H+] = 1e-7 mol/L.
How does pOH relate to pH?
At 25°C, pH + pOH always equals 14.
What do I need to enter into the pH Calculator?
Just 1 value: hydrogen ion concentration [h+]. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the pH Calculator work out the answer?
pH = -log10[H+]. It applies the formula pH = -log10[H+] and shows the working so you can check each step by hand.
Is the pH Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.