HVAC Unit Converter: Temperature, Pressure, Flow & Energy
Temperature Conversion
°C = (°F − 32) × 5/9
°F = °C × 9/5 + 32
K = °C + 273.15 (Kelvin for thermodynamic calculations)
| °F | °C | K | Context |
|---|---|---|---|
| -40 | -40 | 233 | Fahrenheit = Celsius crossover |
| 0 | -17.8 | 255 | Very cold outdoor |
| 32 | 0 | 273 | Water freezes |
| 68 | 20 | 293 | Comfortable indoor |
| 72 | 22.2 | 295 | Typical thermostat setting |
| 98.6 | 37 | 310 | Human body temperature |
| 120 | 48.9 | 322 | Hot water heater setting |
| 140 | 60 | 333 | Hydronic baseboard water |
| 180 | 82.2 | 355 | Standard boiler water |
| 212 | 100 | 373 | Water boils |
Pressure Conversion
| From | To PSI | To Pa | To kPa | To "WC | To bar |
|---|---|---|---|---|---|
| 1 PSI | 1 | 6,895 | 6.895 | 27.68 | 0.0690 |
| 1 Pa | 0.000145 | 1 | 0.001 | 0.00402 | 0.00001 |
| 1 kPa | 0.145 | 1,000 | 1 | 4.02 | 0.01 |
| 1 "WC | 0.0361 | 249 | 0.249 | 1 | 0.00249 |
| 1 bar | 14.50 | 100,000 | 100 | 401.5 | 1 |
| 1 atm | 14.70 | 101,325 | 101.3 | 406.8 | 1.013 |
Airflow Conversion
| From | To CFM | To m³/h | To L/s |
|---|---|---|---|
| 1 CFM | 1 | 1.699 | 0.472 |
| 1 m³/h | 0.589 | 1 | 0.278 |
| 1 L/s | 2.119 | 3.600 | 1 |
Water Flow Conversion
| From | To GPM | To L/s | To m³/h |
|---|---|---|---|
| 1 GPM | 1 | 0.0631 | 0.227 |
| 1 L/s | 15.85 | 1 | 3.600 |
| 1 m³/h | 4.403 | 0.278 | 1 |
Energy and Power Conversion
| From | To BTU/h | To W | To kW | To tons |
|---|---|---|---|---|
| 1 BTU/h | 1 | 0.293 | 0.000293 | 0.0000833 |
| 1 W | 3.412 | 1 | 0.001 | 0.000284 |
| 1 kW | 3,412 | 1,000 | 1 | 0.284 |
| 1 ton | 12,000 | 3,517 | 3.517 | 1 |
| 1 HP | 2,544 | 746 | 0.746 | 0.212 |
Length and Area Conversion
| From | Imperial | Metric |
|---|---|---|
| 1 inch | 1 in | 25.4 mm |
| 1 foot | 1 ft | 0.3048 m |
| 1 yard | 1 yd | 0.9144 m |
| 1 mile | 1 mi | 1.609 km |
| 1 sq ft | 1 ft² | 0.0929 m² |
| 1 sq in | 1 in² | 645.2 mm² |
| 1 sq yd | 1 yd² | 0.836 m² |
Common Mistakes
- Using 1.8 instead of 9/5: The exact factor is 9/5 = 1.8, but rounding can cause errors over large ranges.
- Confusing gauge pressure and absolute: PSI gauge + 14.7 = PSI absolute (PSIA). For gas law calculations, always use absolute pressure.
- Mixing SCFM and CFM: SCFM (standard CFM) is at standard conditions (70°F, 1 atm). Actual CFM varies with temperature and altitude.
Standards Reference
- NIST — Unit definitions and conversion factors
- ASHRAE Fundamentals — Unit conventions
- SI Brochure — International System of Units
Frequently Asked Questions
How do I convert CFM to m³/h?
Multiply CFM by 1.699. Example: 400 CFM × 1.699 = 679.6 m³/h. To convert m³/h to CFM, multiply by 0.589. These conversions are essential when working with international HVAC equipment specifications.
What is 1 ton of cooling in kW?
1 ton of cooling = 12,000 BTU/h = 3.517 kW. This is a measure of cooling capacity, not electrical power consumption. A 3-ton AC unit provides 36,000 BTU/h (10.55 kW) of cooling but draws only 3–4 kW of electrical power (depending on SEER).
How do I convert inches of water column to PSI?
1 inch of water column ("WC) = 0.0361 PSI. To convert: PSI = "WC × 0.0361. Natural gas pressure is typically measured in "WC: 7" WC = 0.25 PSI. HVAC static pressure is measured in "WC: 0.5" WC = 0.018 PSI.
What's the difference between GPM and L/s?
Both measure water flow rate. 1 GPM = 0.0631 L/s. To convert L/s to GPM: multiply by 15.85. US HVAC uses GPM; international uses L/s or m³/h. For hydronic pipe sizing, GPM is standard in the US.
How do I convert kW to BTU?
Multiply kW by 3,412. Example: 10 kW × 3,412 = 34,120 BTU/h. To convert BTU to kW: divide by 3,412. This is essential for comparing electric and gas heating equipment.