HVAC Unit Conversion Reference Guide
Introduction
In the HVAC (Heating, Ventilation, and Air Conditioning) industry, professionals frequently work with both Imperial and Metric units. Understanding how to convert between these units is essential for accurate system design, load calculations, equipment sizing, and cross-border specifications.
This guide summarizes the most commonly used HVAC units and their conversions, organized by category with usage notes for practical reference.
🌡️ Temperature
| Unit | Conversion Formula |
|---|---|
| °F to °C | (°F − 32) × 5/9 |
| °C to °F | (°C × 9/5) + 32 |
| °C to K | K = °C + 273.15 |
Usage:
Temperature readings are foundational in system performance and comfort control. Most global systems use Celsius (°C), but U.S. systems often use Fahrenheit (°F).
🔥 Heating & Cooling Capacity
| Unit | Converts To |
|---|---|
| 1 Ton of Refrigeration (RT) | = 12,000 BTU/h = 3.517 kW = 12.66 MJ/h |
| 1 kW | = 3412 BTU/h |
| 1 BTU | = 1.055 kJ |
| 1 kWh | = 3412 BTU = 3600 kJ |
Usage:
Used to measure the cooling or heating load of HVAC systems. Tons are more common in U.S. specifications, while kW and kJ are used internationally.
💨 Airflow
| Unit | Converts To |
|---|---|
| 1 CFM (Cubic Feet per Minute) | = 1.699 m³/h = 0.0283 m³/min |
| 1 m³/h | = 0.5886 CFM |
Usage:
Crucial for duct design, ventilation planning, and fan selection. CFM is commonly used in the U.S., whereas m³/h is standard in Europe and Asia.
💨 Air Velocity
| Unit | Converts To |
|---|---|
| 1 FPM (Feet per Minute) | = 0.00508 m/s |
| 1 m/s | = 196.85 FPM |
Usage:
Air velocity is key in determining duct sizing and noise levels. High FPM can lead to whistling ducts; low FPM may cause poor airflow.
⚙️ Pressure
| Unit | Converts To |
|---|---|
| 1 psi | = 6.89476 kPa = 0.06895 bar |
| 1 kPa | = 0.145 psi = 0.01 bar |
| 1 bar | = 100 kPa = 14.5038 psi |
| 1 in.wg | = 0.0361 psi = 0.249 kPa = 0.00249 bar |
| 1 atm | = 101.325 kPa = 14.7 psi = 1.01325 bar |
Usage:
Pressure units are used in refrigerant systems (psi/bar), duct static pressure (in.wg or Pa), and pump discharge pressure.
💧 Liquid Flow Rate
| Unit | Converts To |
|---|---|
| 1 GPM (US gallon/min) | = 3.785 L/min = 0.227 m³/h = 0.0631 L/s |
| 1 L/min | = 0.264 GPM |
| 1 m³/h | = 4.402 GPM |
| 1 L/s | = 15.85 GPM |
Usage:
GPM is critical in chilled/hot water systems, cooling towers, and hydronic balancing.
⚡ Energy & Power
| Unit | Converts To |
|---|---|
| 1 kWh | = 3600 kJ = 3412 BTU |
| 1 BTU | = 1.055 kJ = 0.000293 kWh |
| 1 hp (horsepower) | = 0.7457 kW |
Usage:
Used for calculating energy consumption, equipment efficiency, and power input requirements.
⚖️ Mass
| Unit | Converts To |
|---|---|
| 1 kg | = 2.2046 lbs |
| 1 lb | = 0.4536 kg |
Usage:
Important for equipment shipping weights, refrigerant charge amounts, and structural planning.
📐 Dimension & Area
| Unit | Converts To |
|---|---|
| 1 inch | = 25.4 mm |
| 1 foot | = 0.3048 m |
| 1 ft² | = 0.0929 m² |
| 1 m² | = 10.764 ft² |
Usage:
Used in equipment footprint, room sizing, and insulation surface calculations.
📌 Conclusion
This unit conversion guide is a practical reference for HVAC engineers, technicians, designers, and project managers. Whether you’re reading international specs, converting data for equipment selection, or communicating with global teams, having a reliable set of conversions at hand ensures accuracy and consistency in your work.