BTU Calculator

Use this form to calculate your BTU needs. Read our disclaimer.

Tons Per Car

Tons Per Unit
Ambient Conditions
Summer Fahrenheit Dry Bulb (Degrees F)
Summer Fahrenheit Wet Bulb (Degrees F)
Winter Fahrenheit Dry Bulb (Degrees F)
Humidity Ratio - grains H2O / lb of dry air
Location in Degrees Lattitude
Vehicle Interior Conditions
Cooling Fahrenheit Dry Bulb
Relative Humidity (%)
Heating Fahrenheit Dry Bulb
Humidity Ratio - grains H2O / lb of dry air (inside)
Passenger Data
Max Seated Passengers (x + operator)
Max Standing Passengers
Passenger Sensible heat to latent heat ratio
Car Data
HVAC units per Car
Car Length
Car Width
Car Height
Surface Area Including Windows
Shade Coefficient
Car Window Area Facing North
Car Window Area Facing South
Car Window Area Facing East
Car Window Area Facing West
Car Conductivity - Btu/hr
.517390003: Entire Car K Value - Btu/hr ft^2 deg F
Refridgerant Type
Fresh Air (CFM)
Return Air (CFM)
4100: Total Air Per Unit (CFM)
450: Passenger Standing Heat Value Btu/Air/Pass
450: Passenger Sitting Heat Value
247.5: Sensible heat/ Standing passenger
247.5: Sensible heat/ Seated passenger
202.5: Latent Heat / Standing Passenger
202.5: Latent Heat / Seated Passenger
22522.5: Total Pass Sensible heat load (Qsp)
18427.5: Total Pass Latent heat load (Qlt)
Head Load Calculations
14850: Fresh Air sensible heat (QFS)
12821.4: Fresh Air Latent Heat (QFL)
5123: Qlight Lighting load (btu/hr)
1700: Q equip Equipment Load (btu/hr)
12004.2: Q radiation
Shaded Coeficient SC ?
SHGF North For 40 deg North latitude
SHGF South For 40 deg North latitude
SHGF East For 40 deg North latitude
SHGF West For 40 deg North latitude
SHGF Roof For 40 deg North latitude
Solar Load through Car Faces
Absorption coefficient
External coefficient of convection, hext - BTU/hr ft^2 degF
66.38: Car face area (north facing)
66.38: Car face area (south facing)
362.016: Car face area (east facing)
362.016: Car face area (west facing)
447.984: Car roof area
1932.777972: Total surface area
180: Window surface area
.480152086: K value of the surface (stainless steel)
109.5424017: Surface Temperature (north facing)
109.866859: Surface Temperature (south facing)
140.0413845: Surface Temperature (east facing)
109.2179444: Surface Temperature (west facing)
128.5231516: Surface Temperature (roof)
144.7972765: Solar load north face
155.1399391: Solar load south face
6090.909389: Solar load east face
733.1746487: Solar load west face
5059.840557: Solar load roof
Other Heat Load
30000: CAR BODY HEAT LOAD (Conduction)
Carbody Head Load ?
Motor heat/HP
3: Motor HP
Heat Source
24188.1: Solar Gains
30000: Carbody (conduction gains)
92963: Vehicle Sensible Heat
18427.5: Vehicle Latent Heat
14850: Fresh Air Sensible
12821.4: Fresh Air Latent
31248.9: Total Latent
139062: Total Load
11.59: Converted to Tons
11.88: Load in Tons with 2.5% Margin
11.88: tonsPerCar/m