›Sensible AirCFM · ΔT · sensible loadAir
Q = 1.08 × CFM × ΔT
Enter any two values
The blank field will be solved.
›Total Air / EnthalpyCFM · Δh · total loadAir
Q = 4.5 × CFM × Δh
Enter any two values
Uses the standard 4.5 air constant.
›Hydronic LoadGPM · ΔT · water loadHydronic
Q = 500 × GPM × ΔT
Enter any two values
For water near typical HVAC temperatures.
›Air VelocityCFM · area · FPMAir
Velocity = CFM ÷ Area
Enter any two values
Useful for ducts, grilles, louvers, and face velocity.
›Air ChangesCFM · room volume · ACHAir
ACH = (CFM × 60) ÷ Volume
Enter any two values
Room volume = length × width × height.
›Fan LawsRPM ratio · airflow · static · BHPFan
CFM₂ = CFM₁r · SP₂ = SP₁r² · BHP₂ = BHP₁r³
Enter RPM₁ and RPM₂
Add any known baseline quantities to project them.
›Pump PowerFlow · head · efficiencyHydronic
WHP = GPM × Head ÷ 3960 · BHP = WHP ÷ η
Enter flow and head
Efficiency adds estimated brake horsepower.
›Electrical PowerkW · volts · amps · power factorElectrical
Enter two electrical values
PF is adjustable; default is 0.90.
›Unit ConverterHVAC-focused conversionsConversions
Enter a value
Conversions update instantly.
›Duct Size & VelocityRectangular or round duct · airflow · velocityAir
Area from duct geometry · Velocity = airflow ÷ area
Enter duct size and airflow
Velocity can also be entered to solve airflow.
›Equivalent Round DuctRectangular duct → equivalent round diameterAir
Dₑ = 1.30(ab)^0.625 ÷ (a+b)^0.25
Enter rectangular duct dimensions
Approximate equal-friction equivalent diameter.
›Mixed Air TemperatureOutdoor air + return air mixingAir
Tmix = (OA·Toa + RA·Tra) ÷ (OA + RA)
Enter OA and RA conditions
Also reports outdoor-air percentage.
›Coil Load Split / SHRSensible · total · latent · SHRAir
Qs = 1.08·CFM·ΔT · Qt = 4.5·CFM·Δh
Enter airflow, ΔT, and Δh
Calculates sensible, total, latent, and SHR.
›Shaft Power → Motor InputPump or fan shaft power · motor efficiency · kWPower
Motor kW = BHP × 0.7457 ÷ ηmotor
Enter shaft power
Efficiency is optional; blank assumes ideal conversion.
›Ventilation / Outdoor AirPeople + area breathing-zone airflowAir
Vbz = Rp·Pz + Ra·Az · Voz = Vbz ÷ Ez
Enter ventilation inputs
Basic 62.1-style zone calculation.
Use project/code-required Rp, Ra, and Ez values; this calculator does not select them for you.