HVAC CALCULATOR

Heating Load Calculator

Estimate your home’s heating load and heat loss in BTU/hr using building size, insulation, windows, air leakage, and winter design temperatures.

1. Home Dimensions

Enter the dimensions of the heated portion of your home.

ft
ft
ft

2. Winter Design Temperatures

Use the normal indoor heating setpoint and the local winter outdoor design temperature.

°F
°F
Example: If the indoor design temperature is 70°F and the outdoor design temperature is 20°F, the temperature difference used in the heat-loss calculation is 50°F.

3. Insulation

Select the option that most closely represents the home.

4. Windows & Exterior Doors

sq ft

5. Air Leakage & Ventilation

Air infiltration is often one of the largest contributors to residential heat loss.

CFM
YOUR ESTIMATE

Estimated Heating Load

Approximate heat loss at the selected winter design conditions.

0 BTU/hr
Heated Floor Area 0 sq ft
Home Volume 0 cu ft
Temperature Difference 0°F
Estimated BTU per Sq Ft 0

Estimated Heat-Loss Breakdown

Exterior Walls 0 BTU/hr
Windows 0 BTU/hr
Exterior Doors 0 BTU/hr
Ceiling / Attic 0 BTU/hr
Floor / Foundation 0 BTU/hr
Air Infiltration 0 BTU/hr
Mechanical Ventilation 0 BTU/hr
Total Estimated Heat Loss 0 BTU/hr

How the Heating Load Is Estimated

Heat transfer through walls, windows, doors, ceilings and floors is estimated using:

Heat Loss = Area × U-Factor × ΔT

Air infiltration and ventilation losses use:

Heat Loss = 1.08 × CFM × ΔT
Important: This calculator provides a preliminary residential heating-load estimate for educational purposes. It is not an ACCA Manual J calculation. Final HVAC equipment sizing should be based on a room-by-room professional load calculation and local design conditions.

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