Calculate Capacitance (C), Charge (Q), or Voltage (V) using the fundamental physics formula.
Capacitance (C)
Electric Charge (Q)
Voltage (V)
Result:
Understanding the Capacitance Formula
Capacitance is the ability of a component or circuit to collect and store energy in the form of an electrical charge. In the world of electronics, this is a fundamental property of capacitors.
The relationship between capacitance, charge, and voltage is defined by the following mathematical formula:
C = Q / V
Where:
C (Capacitance): Measured in Farads (F).
Q (Charge): Measured in Coulombs (C).
V (Voltage): Measured in Volts (V).
Common Conversion Units
In practical electronics, a "Farad" is a very large unit. You will often work with smaller variations:
Unit
Abbreviation
Value in Farads
Microfarad
µF
10⁻⁶ F
Nanofarad
nF
10⁻⁹ F
Picofarad
pF
10⁻¹² F
Example Calculation
Suppose you have a capacitor that stores 0.02 Coulombs of charge when connected to a 10-Volt battery. To find the capacitance:
C = Q / V
C = 0.02 C / 10 V C = 0.002 Farads (or 2mF)
How to use this calculator
1. Select the variable you want to solve for (Capacitance, Charge, or Voltage).
2. Enter the two known values in the provided input fields.
3. Click "Calculate Now" to see the result instantly.
function updateLabels() {
var mode = document.getElementById("calcMode").value;
var label1 = document.getElementById("label1");
var label2 = document.getElementById("label2");
var val1 = document.getElementById("val1");
var val2 = document.getElementById("val2");
// Reset result box
document.getElementById("resultBox").style.display = "none";
val1.value = "";
val2.value = "";
if (mode === "C") {
label1.innerText = "Electric Charge (Q) in Coulombs";
label2.innerText = "Voltage (V) in Volts";
val1.placeholder = "e.g. 0.01";
val2.placeholder = "e.g. 5";
} else if (mode === "Q") {
label1.innerText = "Capacitance (C) in Farads";
label2.innerText = "Voltage (V) in Volts";
val1.placeholder = "e.g. 0.0001";
val2.placeholder = "e.g. 12";
} else if (mode === "V") {
label1.innerText = "Electric Charge (Q) in Coulombs";
label2.innerText = "Capacitance (C) in Farads";
val1.placeholder = "e.g. 0.05";
val2.placeholder = "e.g. 0.002";
}
}
function performCalculation() {
var mode = document.getElementById("calcMode").value;
var v1 = parseFloat(document.getElementById("val1").value);
var v2 = parseFloat(document.getElementById("val2").value);
var resultDisplay = document.getElementById("resultDisplay");
var resultBox = document.getElementById("resultBox");
var result = 0;
var unit = "";
if (isNaN(v1) || isNaN(v2)) {
alert("Please enter valid numeric values.");
return;
}
if (mode === "C") {
// C = Q / V
if (v2 === 0) {
alert("Voltage cannot be zero.");
return;
}
result = v1 / v2;
unit = " Farads (F)";
} else if (mode === "Q") {
// Q = C * V
result = v1 * v2;
unit = " Coulombs (C)";
} else if (mode === "V") {
// V = Q / C
if (v2 === 0) {
alert("Capacitance cannot be zero.");
return;
}
result = v1 / v2;
unit = " Volts (V)";
}
// Handle very small numbers by showing scientific notation if needed
var finalString = "";
if (result < 0.000001 && result !== 0) {
finalString = result.toExponential(4) + unit;
} else {
finalString = result.toLocaleString(undefined, { maximumFractionDigits: 8 }) + unit;
}
resultDisplay.innerText = finalString;
resultBox.style.display = "block";
}