Use this calculator to estimate the appropriate air conditioning tonnage required for your room or space. Selecting the correct AC size is crucial for efficient cooling, humidity control, and energy savings.
Average
Good
Poor
Indirect (North-facing or shaded)
Partial (East/West-facing)
Direct (South-facing, unshaded)
function calculateACTons() {
var roomLength = parseFloat(document.getElementById("roomLength").value);
var roomWidth = parseFloat(document.getElementById("roomWidth").value);
var ceilingHeight = parseFloat(document.getElementById("ceilingHeight").value);
var insulationQuality = document.getElementById("insulationQuality").value;
var numOccupants = parseInt(document.getElementById("numOccupants").value);
var windowArea = parseFloat(document.getElementById("windowArea").value);
var sunExposure = document.getElementById("sunExposure").value;
if (isNaN(roomLength) || roomLength <= 0 ||
isNaN(roomWidth) || roomWidth <= 0 ||
isNaN(ceilingHeight) || ceilingHeight <= 0 ||
isNaN(numOccupants) || numOccupants < 0 ||
isNaN(windowArea) || windowArea 8) {
ceilingAdjFactor = (ceilingHeight – 8) * 0.05;
}
// Insulation Adjustment
var insulationAdjFactor = 0;
if (insulationQuality === 'poor') {
insulationAdjFactor = 0.20; // 20% increase for poor insulation
} else if (insulationQuality === 'good') {
insulationAdjFactor = -0.10; // 10% decrease for good insulation
}
// Occupant Load: 600 BTUs per person
var occupantBTU = numOccupants * 600;
// Window Heat Gain: 40 BTUs per square foot of window
var windowBTU = windowArea * 40;
// Sun Exposure Adjustment
var sunAdjFactor = 0;
if (sunExposure === 'direct') {
sunAdjFactor = 0.15; // 15% increase for direct sun
} else if (sunExposure === 'partial') {
sunAdjFactor = 0.05; // 5% increase for partial sun
}
// Total BTU Calculation
var totalBTU = baseBTU * (1 + ceilingAdjFactor + insulationAdjFactor + sunAdjFactor) + occupantBTU + windowBTU;
// Convert to Tons (1 Ton = 12,000 BTUs)
var requiredTons = totalBTU / 12000;
document.getElementById("result").innerHTML =
"Estimated Required AC Tonnage: " + requiredTons.toFixed(2) + " tons" +
"(Equivalent to " + totalBTU.toFixed(0) + " BTUs/hour)";
}
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background-color: #f9f9f9;
border: 1px solid #ddd;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
font-family: Arial, sans-serif;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.calculator-container p {
margin-bottom: 15px;
line-height: 1.6;
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.calc-input-group {
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display: block;
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.calc-input-group input[type="number"],
.calc-input-group select {
width: calc(100% – 22px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
}
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width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
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border-radius: 4px;
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cursor: pointer;
margin-top: 20px;
transition: background-color 0.3s ease;
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.calculate-button:hover {
background-color: #0056b3;
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.calculator-result {
margin-top: 25px;
padding: 15px;
border: 1px solid #28a745;
background-color: #e2f0e5;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
color: #28a745;
text-align: center;
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.calculator-result p {
margin: 5px 0;
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color: #dc3545;
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}
Understanding AC Tonnage and Why it Matters
Air conditioning capacity is measured in "tons," which is a unit derived from the amount of heat required to melt one ton of ice in 24 hours. One ton of cooling capacity is equivalent to 12,000 British Thermal Units (BTUs) per hour. BTUs represent the amount of heat an AC unit can remove from a space in one hour.
Why Proper Tonnage is Crucial:
Too Small: An undersized AC unit will struggle to cool your space effectively, running constantly without reaching the desired temperature. This leads to higher energy bills, increased wear and tear on the unit, and uncomfortable indoor conditions.
Too Large: An oversized AC unit will cool the space too quickly, causing it to "short cycle" – turning on and off frequently. While it might seem powerful, this leads to poor humidity removal (leaving your home feeling clammy), uneven cooling, higher energy consumption due to frequent starts, and reduced lifespan of the unit.
Factors Influencing AC Tonnage Requirements:
The ideal AC tonnage for a room or home is not just about square footage. Several factors contribute to the heat load of a space:
Room Size (Length x Width x Height): Larger rooms and those with higher ceilings naturally require more cooling capacity to manage a greater volume of air.
Insulation Quality: Well-insulated walls, ceilings, and floors prevent heat from entering or escaping, reducing the cooling load. Poor insulation means more heat transfer, requiring a larger AC unit.
Number of Occupants: Each person generates body heat. More people in a room mean a higher heat load that the AC must overcome.
Window Area and Sun Exposure: Windows are significant sources of heat gain, especially those facing direct sunlight. Larger windows or those with direct sun exposure will increase the cooling demand.
Climate and Local Temperature: Homes in hotter climates or those exposed to intense summer heat will require more powerful cooling systems.
Heat-Generating Appliances: Appliances like refrigerators, ovens, computers, and lighting fixtures all contribute to the heat load within a room, particularly in kitchens or home offices.
Our AC Ton Calculator takes these critical factors into account to provide a more accurate estimate than a simple square footage calculation. Remember, this calculator provides an estimate. For precise sizing and installation, always consult with a qualified HVAC professional who can perform a detailed heat load calculation (Manual J) specific to your home's unique characteristics.