Estimate the cooling and heating capacity needed for your space.
Good (Newer Home, Double Pane)
Average (Standard/Common)
Poor (Older Home, Drafty)
Mostly Shady
Average Sunlight
High Sunlight / Many Windows
No
Yes
Estimated HVAC Load Requirements:
Your space requires approximately:
0 BTU/hr
Recommended Unit Size:
0 Tons
*Note: This is a preliminary estimate. A professional Manual J load calculation is recommended before purchase.
How HVAC Load Calculation Works
Choosing the right HVAC system is not just about the size of your home; it's about the "load." An HVAC load calculation determines exactly how much heating and cooling (measured in BTUs) your home needs to maintain a comfortable temperature. Getting this right is crucial: a system that is too small won't keep you comfortable, while an oversized system will cycle on and off too frequently, leading to high energy bills and premature wear.
Key Factors in BTU Calculation
Square Footage: The primary driver. More space requires more air volume movement.
Ceiling Height: A room with 12-foot ceilings has 50% more air to cool than one with 8-foot ceilings.
Insulation: "Poor" insulation (common in homes built before 1980) allows heat to transfer quickly, requiring higher capacity.
Occupancy: Every human body generates about 600 BTUs of heat per hour.
The Kitchen Factor: Ovens and stovetops generate significant heat loads. If the calculated area includes a kitchen, we add roughly 4,000 BTUs to the requirement.
HVAC Sizing Chart (Standard Estimates)
Square Footage
BTU Capacity
Tonnage
600 – 1,000
18,000
1.5 Tons
1,001 – 1,500
24,000
2.0 Tons
1,501 – 2,000
30,000
2.5 Tons
2,001 – 2,500
36,000
3.0 Tons
Why "Tons" Matter
In the HVAC industry, cooling capacity is often measured in Tons. One ton of cooling is equivalent to 12,000 BTUs per hour. This term originates from the amount of heat required to melt one ton of ice in a 24-hour period. If our calculator suggests 30,000 BTUs, you would typically look for a 2.5-ton unit.
function calculateHVAC() {
var sqft = parseFloat(document.getElementById('hvac_sqft').value);
var insulation = document.getElementById('hvac_insulation').value;
var sun = document.getElementById('hvac_sun').value;
var occupants = parseInt(document.getElementById('hvac_occupants').value);
var kitchen = document.getElementById('hvac_kitchen').value;
var ceilingHeight = parseFloat(document.getElementById('hvac_ceiling').value);
if (isNaN(sqft) || sqft 2) {
baseBTU += (occupants – 2) * 600;
}
// Add for Kitchen
if (kitchen === 'yes') {
baseBTU += 4000;
}
// Final calculations
var finalBTU = Math.round(baseBTU);
var tonnage = (finalBTU / 12000).toFixed(2);
// Display Results
document.getElementById('hvac_btu_display').innerText = finalBTU.toLocaleString() + " BTU/hr";
document.getElementById('hvac_ton_display').innerText = tonnage + " Tons";
document.getElementById('hvac_result_box').style.display = 'block';
// Smooth scroll to result
document.getElementById('hvac_result_box').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}