Professional pH Calculator
Calculation Type
Hydrogen Ion Concentration [H+] to pH
Hydroxide Ion Concentration [OH-] to pH
pOH to pH
[H+] Concentration (mol/L)
[OH-] Concentration (mol/L)
pOH Value
Calculate Result
Results
—
—
pOH: —
[H+]: — mol/L
[OH-]: — mol/L
Nature: —
Understanding the pH Scale
The pH scale is a logarithmic measurement used to specify the acidity or basicity (alkalinity) of an aqueous solution. Ranging typically from 0 to 14, pH values represent the "power of hydrogen." A pH of 7 is considered neutral (like pure water at 25°C). Values below 7 indicate acidity, while values above 7 indicate an alkaline or basic solution.
How pH is Calculated
The mathematical definition of pH is the negative base-10 logarithm of the molar concentration of hydrogen ions ([H+]) in a solution. The formula is expressed as:
pH = -log10([H+])
Similarly, pOH measures the concentration of hydroxide ions ([OH-]):
pOH = -log10([OH-])
Practical Examples of pH Levels
Substance
Typical pH
Classification
Battery Acid 0.0 – 1.0 Strongly Acidic Lemon Juice 2.0 – 3.0 Acidic Pure Water 7.0 Neutral Baking Soda 8.0 – 9.0 Alkaline Bleach 11.0 – 13.0 Strongly Alkaline
Why pH Matters
Biological Systems: Human blood must stay within a very narrow range (7.35 to 7.45) for survival.Agriculture: Soil pH affects nutrient availability for crops. Most plants prefer slightly acidic to neutral soil (6.0 to 7.0).Industrial Use: Water treatment facilities monitor pH to prevent pipe corrosion and ensure safe drinking water.Skin Care: The human skin has a natural "acid mantle" with a pH around 5.5, which helps protect against bacteria.
function toggleInputs() {
var type = document.getElementById("calcType").value;
document.getElementById("input-container-h").style.display = (type === "h_to_ph") ? "block" : "none";
document.getElementById("input-container-oh").style.display = (type === "oh_to_ph") ? "block" : "none";
document.getElementById("input-container-poh").style.display = (type === "poh_to_ph") ? "block" : "none";
}
function calculatePH() {
var type = document.getElementById("calcType").value;
var ph = 0;
var oh = 0;
var h = 0;
var poh = 0;
var kw = 1e-14;
if (type === "h_to_ph") {
h = parseFloat(document.getElementById("h_val").value);
if (isNaN(h) || h <= 0) { alert("Please enter a valid positive concentration for [H+]."); return; }
ph = -Math.log10(h);
poh = 14 – ph;
oh = kw / h;
} else if (type === "oh_to_ph") {
oh = parseFloat(document.getElementById("oh_val").value);
if (isNaN(oh) || oh <= 0) { alert("Please enter a valid positive concentration for [OH-]."); return; }
poh = -Math.log10(oh);
ph = 14 – poh;
h = kw / oh;
} else if (type === "poh_to_ph") {
poh = parseFloat(document.getElementById("poh_val").value);
if (isNaN(poh)) { alert("Please enter a valid pOH value."); return; }
ph = 14 – poh;
h = Math.pow(10, -ph);
oh = Math.pow(10, -poh);
}
// Classification
var classification = "";
var color = "";
if (ph 7.5) {
classification = "Alkaline (Basic)";
color = "#27ae60";
} else {
classification = "Neutral";
color = "#f39c12";
}
// Display Results
document.getElementById("ph-results").style.display = "block";
document.getElementById("main-ph-display").innerText = ph.toFixed(2);
document.getElementById("classification").innerText = classification;
document.getElementById("classification").style.color = color;
document.getElementById("res-poh").innerText = poh.toFixed(2);
document.getElementById("res-h").innerText = h.toExponential(4);
document.getElementById("res-oh").innerText = oh.toExponential(4);
document.getElementById("res-nature").innerText = classification;
// Scroll to result
document.getElementById("ph-results").scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}