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HVAC Conversions — BTU/hr, kW, Ton, ACH, CFM
Free HVAC and ventilation unit conversion calculators. Convert BTU/hr to kW, tons of refrigeration to kW, airflow ACH to CFM, wet bulb to relative humidity, and more industrial HVAC engineering tools.
HVAC and ventilation unit conversion connects thermal power (BTU/hr, kW, tons) with airflow (CFM, ACH, velocity) and psychrometric properties (wet bulb, relative humidity). Our calculators are built on formulas from ASHRAE Fundamentals, ASHRAE 62.1, AHRI 550/590, and ASHRAE 90.1.
Engineers frequently need to bridge US and international equipment specifications: a chiller rated in tons (RT) must be compared against a European competitor's kW bid, a boiler rated in BTU/hr input must be converted to kW net output for energy modeling, and air changes per hour (ACH) must be converted to CFM for duct sizing. Every conversion below handles these cross-system transitions accurately.
Common HVAC Conversions (Quick Reference)
| From | To | Multiply by |
|---|---|---|
| BTU/hr | kW | 0.00029307 |
| kW | BTU/hr | 3,412.14 |
| Ton refrig. | kW | 3.51685 |
| BTU/hr | Watt | 0.29307 |
| CFM | ACH (10 ft ceiling) | Depends on volume |
| m/s | FPM | 196.85 |
| FPM | m/s | 0.00508 |
| CFM/ton | m³/h/kW | 0.0483 |
HVAC Conversions — BTU/hr, kW, Ton, ACH, CFM (16)
BTU/hr to kW Calculator (×0.000293) | Chiller & Boiler Converter
1 BTU per hour equals 0.000293071 kW. A British Thermal Unit (BTU) is defined as the amount of heat required...
BTU/hr to Watts Converter | Free Online Calculator
1 BTU/hr = 0.293071 W exactly, derived from 1 BTU (International Table) = 1,055.05585262 J and 1 hour = 3,600...
CFM per Ton Converter | Free Online Calculator
The 400 CFM per ton rule of thumb in HVAC derives directly from the psychrometric heat balance of standard air...
EER to kW/Ton Calculator | HVAC Efficiency Converter
EER (Energy Efficiency Ratio) is the cooling capacity in BTU per hour divided by the electrical power input in...
FPM to m/s Converter | Free Online Calculator
1 foot per minute = 0.00508 meters per second, derived from 1 ft = 0.3048 m (1959 international yard...
kW to BTU/hr Converter | Free Online Calculator
1 kW equals exactly 3,412.141156 BTU per hour. The conversion factor traces back to the definitions of the...
m/s to FPM Calculator (×196.85) | Duct Velocity & HVAC Tool
1 m/s = 196.8504 fpm exactly, derived from 1 m = 3.28084 ft and 1 minute = 60 seconds, giving 3.28084 × 60 =...
Refrigeration Tons to kW Converter | Free Online Calculator
One refrigeration ton (RT) equals 3.51685 kW. This unit traces its origin to the 19th-century ice trade, where...
Sensible Heat Calculator | Free Online Calculator
Sensible heat is the portion of the cooling (or heating) load that changes the air temperature, measurable...
ACH to CFM Calculator | Free Online Calculator
Air Changes per Hour (ACH) is a dilution ventilation metric that expresses how many times the entire volume of...
Air Changes Per Hour (ACH) Calculator | Free Online Calculator
Air Changes Per Hour (ACH) is the number of times the total air volume in a room or zone is replaced with...
Duct Velocity to CFM Calculator | Free Online Calculator
The fundamental relationship between air velocity and volumetric flow: CFM = Velocity × Area. If air moves at...
HVAC Load Calculator (Tons) | Free Online Calculator
HVAC cooling load in refrigeration tons is the total heat removal rate of the cooling coil, comprising...
Latent Heat Calculator | Free Online Calculator
Latent heat in HVAC is the energy associated with moisture removal (or addition) to the air, manifested as the...
Static Pressure to CFM Calculator | Free Online Calculator
This formula converts a static pressure differential across a known opening or flow resistance into an...
Wet Bulb to Relative Humidity Calculator | Free Online Calculator
The wet bulb temperature is the temperature a parcel of air reaches when it is cooled adiabatically to...
Frequently Asked Questions
What is a refrigeration ton?
1 refrigeration ton (RT) = 12,000 BTU/hr = 3.51685 kW. It originates from the cooling effect of melting 1 ton (2,000 lbs) of ice at 32°F over 24 hours. Modern chillers range from 10 to 2,000+ tons.
How do I convert Air Changes per Hour to CFM?
CFM = (ACH × Room Volume in ft³) ÷ 60. For a 10,000 ft³ room requiring 6 ACH, the required airflow is (6 × 10,000) ÷ 60 = 1,000 CFM. ACH requirements vary by space type: offices typically 4-6 ACH, laboratories 6-12 ACH, cleanrooms 20+ ACH.
Why do US HVAC specs use BTU/hr while international uses kW?
BTU/hr persists in North America through legacy standards, equipment catalogs, and building codes (ASHRAE 90.1). The conversion is straightforward (1 kW = 3,412 BTU/hr), but US practitioners are most comfortable with BTU/hr and tons. International harmonization is slowly shifting the industry toward kW.
What is the typical duct velocity for HVAC?
Residential branches: 600-900 FPM (3-4.5 m/s). Main ducts: 700-1,000 FPM (3.5-5 m/s). Commercial low-pressure: 1,000-1,500 FPM (5-7.6 m/s). Higher velocities increase noise and pressure drop but reduce duct size and cost.
How does latent heat differ from sensible heat?
Sensible heat changes air temperature (measureable with a thermometer). Latent heat changes moisture content (humidity) without changing temperature — it's the energy to evaporate or condense water. In cooling, about 30% of the load is latent (dehumidification) and 70% is sensible (temperature reduction). Both must be calculated for proper equipment sizing.