.ac-btu-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #f9f9f9;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
color: #333;
}
.ac-btu-calculator-container h2 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 1.8em;
}
.ac-btu-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-direction: column;
}
.ac-btu-calculator-container label {
margin-bottom: 8px;
font-weight: bold;
color: #555;
font-size: 0.95em;
}
.ac-btu-calculator-container input[type="number"],
.ac-btu-calculator-container select {
width: 100%;
padding: 12px;
border: 1px solid #ccc;
border-radius: 6px;
box-sizing: border-box;
font-size: 1em;
color: #333;
background-color: #fff;
transition: border-color 0.3s ease;
}
.ac-btu-calculator-container input[type="number"]:focus,
.ac-btu-calculator-container select:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25);
}
.ac-btu-calculator-container button {
width: 100%;
padding: 14px;
background-color: #28a745;
color: white;
border: none;
border-radius: 6px;
font-size: 1.1em;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 20px;
}
.ac-btu-calculator-container button:hover {
background-color: #218838;
transform: translateY(-2px);
}
.ac-btu-calculator-container #btuResult {
margin-top: 25px;
padding: 18px;
border: 1px solid #d4edda;
background-color: #e9f7ef;
border-radius: 8px;
text-align: center;
font-size: 1.3em;
font-weight: bold;
color: #155724;
min-height: 30px;
display: flex;
align-items: center;
justify-content: center;
}
.ac-btu-calculator-container .calculator-article {
margin-top: 30px;
line-height: 1.7;
color: #444;
font-size: 0.95em;
}
.ac-btu-calculator-container .calculator-article h3 {
color: #2c3e50;
margin-top: 25px;
margin-bottom: 15px;
font-size: 1.4em;
}
.ac-btu-calculator-container .calculator-article p {
margin-bottom: 15px;
}
.ac-btu-calculator-container .calculator-article ul {
list-style-type: disc;
margin-left: 20px;
margin-bottom: 15px;
}
.ac-btu-calculator-container .calculator-article ul li {
margin-bottom: 8px;
}
function calculateBTU() {
var roomLength = parseFloat(document.getElementById("roomLength").value);
var roomWidth = parseFloat(document.getElementById("roomWidth").value);
var insulationQuality = document.getElementById("insulationQuality").value;
var sunExposure = document.getElementById("sunExposure").value;
var numOccupants = parseInt(document.getElementById("numOccupants").value);
var numAppliances = parseInt(document.getElementById("numAppliances").value);
var windowArea = parseFloat(document.getElementById("windowArea").value);
var isKitchen = document.getElementById("isKitchen").value;
var resultDiv = document.getElementById("btuResult");
// Input validation
if (isNaN(roomLength) || roomLength <= 0 ||
isNaN(roomWidth) || roomWidth <= 0 ||
isNaN(numOccupants) || numOccupants < 0 ||
isNaN(numAppliances) || numAppliances < 0 ||
isNaN(windowArea) || windowArea < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
var squareFootage = roomLength * roomWidth;
var baseBTU = squareFootage * 20; // Standard starting point: 20 BTU per square foot
var totalBTU = baseBTU;
// Adjustments based on factors
// Sun Exposure
if (sunExposure === "medium") {
totalBTU *= 1.05; // +5% for medium sun
} else if (sunExposure === "high") {
totalBTU *= 1.10; // +10% for high sun
}
// Occupants
totalBTU += numOccupants * 600; // Each person adds ~600 BTU/hr
// Heat-Generating Appliances
totalBTU += numAppliances * 1200; // Each major appliance adds ~1200 BTU/hr
// Window Area
totalBTU += windowArea * 50; // Rough estimate for heat gain through windows
// Kitchen
if (isKitchen === "yes") {
totalBTU += 4000; // Add extra BTU for kitchens
}
// Insulation Quality (applied last as a multiplier to the total)
if (insulationQuality === "poor") {
totalBTU *= 1.10; // +10% for poor insulation
} else if (insulationQuality === "good") {
totalBTU *= 0.90; // -10% for good insulation
}
// Round to nearest 100 for common AC unit sizes
var recommendedBTU = Math.round(totalBTU / 100) * 100;
// Provide a range for flexibility
var minBTU = Math.round((recommendedBTU * 0.95) / 100) * 100;
var maxBTU = Math.round((recommendedBTU * 1.05) / 100) * 100;
resultDiv.innerHTML = "Recommended BTU: " + recommendedBTU.toLocaleString() + " BTU/hr(Approximate Range: " + minBTU.toLocaleString() + " – " + maxBTU.toLocaleString() + " BTU/hr)";
}
AC Unit BTU Calculator
Average
Poor
Good
Low (North-facing, shaded)
Medium (East/West-facing)
High (South-facing, unshaded)
No
Yes
Understanding BTU for AC Units
BTU stands for British Thermal Unit, and it's a measure of heat energy. When it comes to air conditioning, BTU refers to the amount of heat an AC unit can remove from a room per hour. Choosing the right BTU capacity for your AC unit is crucial for both comfort and energy efficiency.
Why Proper BTU Sizing Matters
- Too Low BTU: An AC unit with insufficient BTU will struggle to cool the room effectively, running constantly without reaching the desired temperature. This leads to higher energy bills and a lack of comfort.
- Too High BTU: An oversized AC unit will cool the room too quickly, causing it to cycle on and off frequently (short-cycling). While it might seem powerful, this prevents the unit from running long enough to adequately remove humidity from the air, leaving the room feeling damp and clammy. Short-cycling also puts more wear and tear on the compressor, shortening the unit's lifespan and wasting energy.
Factors Influencing BTU Needs
Our calculator takes several key factors into account to provide a more accurate BTU recommendation than simply using square footage:
- Room Size (Length & Width): The larger the room, the more BTUs are needed to cool it.
- Insulation Quality: Well-insulated rooms retain cool air better, requiring fewer BTUs. Poorly insulated rooms lose cool air quickly, demanding more powerful cooling.
- Sun Exposure: Rooms that receive direct sunlight (especially south or west-facing) absorb more heat, necessitating higher BTU capacity.
- Number of Occupants: Each person generates body heat, contributing to the room's heat load. More people mean more BTUs are required.
- Heat-Generating Appliances: Electronics like large TVs, computers, and kitchen appliances (ovens, refrigerators) emit heat, increasing the cooling demand.
- Window Area: Windows are a significant source of heat gain, especially if they are old, single-pane, or exposed to direct sunlight. Larger window areas generally require more BTUs.
- Room Type (Kitchen): Kitchens typically generate a lot of heat from cooking appliances, requiring a higher BTU capacity compared to other rooms of similar size.
How to Use This Calculator
Simply input the details of your room into the respective fields. The calculator will then provide an estimated BTU range suitable for your specific conditions. Remember, this is an estimate, and professional HVAC consultation is always recommended for precise sizing and installation.