.calc-container {
max-width: 600px;
margin: 20px auto;
padding: 25px;
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
font-family: Arial, sans-serif;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 20px;
font-size: 24px;
font-weight: bold;
}
.form-group {
margin-bottom: 20px;
}
.form-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #495057;
}
.form-group input {
width: 100%;
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box; /* Ensures padding doesn't affect width */
}
.form-group input:focus {
border-color: #007bff;
outline: none;
}
.calc-btn {
display: block;
width: 100%;
padding: 14px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
cursor: pointer;
transition: background-color 0.3s;
font-weight: bold;
}
.calc-btn:hover {
background-color: #0056b3;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #ffffff;
border-left: 5px solid #28a745;
border-radius: 4px;
display: none;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.result-item {
margin-bottom: 10px;
font-size: 18px;
color: #333;
}
.result-value {
font-weight: bold;
color: #28a745;
font-size: 24px;
}
.error-msg {
color: #dc3545;
margin-top: 10px;
display: none;
text-align: center;
}
.content-section {
max-width: 800px;
margin: 40px auto;
font-family: Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.content-section h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.content-section h3 {
color: #007bff;
margin-top: 25px;
}
.content-section p {
margin-bottom: 15px;
}
.formula-box {
background-color: #e9ecef;
padding: 15px;
border-radius: 5px;
font-family: 'Courier New', Courier, monospace;
font-weight: bold;
text-align: center;
margin: 20px 0;
}
table {
width: 100%;
border-collapse: collapse;
margin: 20px 0;
}
table, th, td {
border: 1px solid #ddd;
}
th, td {
padding: 12px;
text-align: left;
}
th {
background-color: #f2f2f2;
}
function calculateWattHours() {
// Get input values
var ahInput = document.getElementById("ahInput").value;
var voltageInput = document.getElementById("voltageInput").value;
var resultBox = document.getElementById("resultBox");
var errorMsg = document.getElementById("errorMsg");
// Reset display
resultBox.style.display = "none";
errorMsg.style.display = "none";
// Validate inputs
if (ahInput === "" || voltageInput === "") {
errorMsg.innerHTML = "Please enter both Amp Hours and Voltage.";
errorMsg.style.display = "block";
return;
}
var ah = parseFloat(ahInput);
var voltage = parseFloat(voltageInput);
if (isNaN(ah) || isNaN(voltage) || ah < 0 || voltage < 0) {
errorMsg.innerHTML = "Please enter valid positive numbers.";
errorMsg.style.display = "block";
return;
}
// Calculation: Wh = Ah * V
var wattHours = ah * voltage;
// Calculation: kWh = Wh / 1000
var kiloWattHours = wattHours / 1000;
// Display results
document.getElementById("whResult").innerHTML = wattHours.toFixed(2) + " Wh";
document.getElementById("kwhResult").innerHTML = kiloWattHours.toFixed(3) + " kWh";
resultBox.style.display = "block";
}
Understanding the Amp Hours to Watt Hours Conversion
Whether you are sizing a solar panel system, choosing a battery for your RV, or comparing laptop battery capacities, understanding the relationship between Amp Hours (Ah) and Watt Hours (Wh) is crucial. This calculator allows you to convert electric charge capacity into total energy capacity.
The Conversion Formula
The calculation to convert Amp Hours to Watt Hours is straightforward multiplication. Watt hours represents energy, while Amp hours represents charge. To get energy, you must account for the voltage (electrical pressure) at which the charge is delivered.
Watt Hours (Wh) = Amp Hours (Ah) × Voltage (V)
Similarly, if you need to determine Kilowatt Hours (kWh), which is the standard billing unit for electricity, you divide the Watt Hours by 1,000.
Kilowatt Hours (kWh) = (Ah × V) / 1000
Real-World Calculation Examples
Different applications use different standard voltages. Here are a few examples of how this math applies to real-life scenarios:
| Device/System |
Capacity (Ah) |
Voltage (V) |
Energy (Wh) |
| Car Battery |
60 Ah |
12 V |
720 Wh |
| Power Tool Battery |
5 Ah |
18 V |
90 Wh |
| USB Power Bank |
20 Ah (20,000 mAh) |
3.7 V |
74 Wh |
| E-Bike Battery |
14 Ah |
36 V |
504 Wh |
Why Watt Hours Matter More Than Amp Hours
Consumers often get confused when comparing batteries solely based on Amp Hours. For example, a 20Ah power bank seems larger than a 5Ah power tool battery. However, because the power tool battery operates at 18V and the power bank cells usually operate at 3.7V, the energy difference isn't as massive as the Ah rating suggests.
Watt Hours is the great equalizer because it measures total work energy. This is why airlines regulate lithium batteries based on Watt Hours (usually a 100Wh limit) rather than Amp Hours.
Frequently Asked Questions
How do I convert milliamp hours (mAh) to Watt Hours?
Small electronics often use mAh. To convert, first divide mAh by 1,000 to get Ah, then multiply by voltage.
Formula: (mAh / 1000) × V = Wh.
Does voltage drop affect the calculation?
Technically, yes. A 12V battery doesn't stay at 12V exactly as it drains; it drops lower. However, for nominal capacity ratings, we use the nominal voltage (e.g., 12V, 24V, 48V) to estimate total energy storage.
Why do I need to know Wh?
You need to know Watt Hours to calculate how long a battery will power a specific appliance. If you have a light bulb that draws 10 Watts, and a battery with 100 Wh of energy, the battery will theoretically last 10 hours (100 Wh / 10 W = 10 h).