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pH Calculator
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This pH Calculator computes pH and pOH from a given hydrogen ion [H+] or hydroxide ion [OH-] concentration in mol/L, using the standard pH = -log[H+] relationship, and classifies the result as acidic, neutral, or basic. It's built for chemistry students checking homework, verifying lab calculations, or building intuition for how concentration relates to pH on the logarithmic scale. Choose whether your known concentration is [H+] or [OH-], enter the value, and get both pH and pOH (which always sum to 14 at 25°C) along with the classification. Everything runs locally in your browser. Scroll down to enter your concentration.
Features
- Calculates pH and pOH from either [H+] or [OH-]
- Classifies the result as acidic, neutral, or basic
- Uses the standard -log10 relationship
- Instant recalculation as you change inputs
Why use this ph calculator?
- Quick way to check chemistry homework or lab math
- No manual logarithm calculation required
- Fully private — nothing uploaded
- Free with unlimited use
Frequently asked questions
How is pH calculated from concentration?
pH = -log10[H+], where [H+] is the hydrogen ion concentration in moles per liter.
Why do pH and pOH add up to 14?
At 25°C, the ion product of water (Kw) is 10⁻¹⁴, so pH + pOH = 14 for any aqueous solution at that standard temperature.
What pH range is considered acidic vs basic?
A pH below 7 is acidic, exactly 7 is neutral (like pure water at 25°C), and above 7 is basic (alkaline).
Can I enter [OH-] instead of [H+]?
Yes, switch the mode to hydroxide ion concentration and the calculator will compute pOH first, then derive pH from it.
Does this account for temperature other than 25°C?
No, it assumes the standard 25°C ion product of water (Kw = 10⁻¹⁴); pH/pOH relationships shift slightly at other temperatures.