Fan Calculator
Calculate fan performance including CFM, power consumption, efficiency, and static pressure
Fan Performance Calculator
High airflow, low pressure, propeller-like blades
Applications: Cooling, ventilation, exhaust fans
Cubic Feet per Minute - volume flow rate
Pressure difference across the fan
Ratio of air power to shaft power (typical: 40-85%)
Shaft power required to drive the fan
Electrical Properties (Optional)
Fan Performance Results
Formula: Air Power = Airflow × Static Pressure
Shaft Power: Air Power ÷ Fan Efficiency
Airflow conversion: 0 CFM = 0.0000 m³/s
Pressure conversion: 0.00 PA = 0.0 Pa
Fan Performance Characteristics
Typical Efficiency by Type
- • Axial fans: 40-60%
- • Centrifugal fans: 60-85%
- • Mixed flow fans: 50-70%
Pressure Range by Type
- • Axial fans: 0-500 Pa
- • Centrifugal fans: 500-5000 Pa
- • Mixed flow fans: 200-2000 Pa
Example Calculation
HVAC System Fan
Type: Centrifugal fan for office building
Airflow: 2000 CFM (0.944 m³/s)
Static Pressure: 250 Pa (1.0 in H₂O)
Fan Efficiency: 75%
Calculation
Air Power = 0.944 m³/s × 250 Pa = 236 W
Shaft Power = 236 W ÷ 0.75 = 315 W
Required motor: ~0.5 HP (allowing for safety factor)
Fan Selection Guide
Determine Requirements
Calculate required CFM and pressure
Choose Fan Type
Axial for high flow, centrifugal for high pressure
Calculate Power
Size motor based on shaft power requirements
Unit Conversions
Airflow
1 CFM = 0.000471947 m³/s
1 CFM = 28.317 L/min
Pressure
1 in H₂O = 249.09 Pa
1 mmHg = 133.32 Pa
1 PSI = 6894.76 Pa
Power
1 HP = 745.7 W
1 kW = 1000 W
Fan Tips
Higher efficiency fans reduce operating costs
Variable speed drives can improve efficiency
Proper ductwork design reduces pressure losses
Regular maintenance maintains performance
Understanding Fan Performance
What is CFM?
CFM stands for Cubic Feet per Minute, which measures the volume flow rate of air. It represents how much air the fan can move in one minute under specific conditions. Higher CFM means more air movement, making it crucial for ventilation and cooling applications.
Static Pressure
Static pressure is the resistance that air encounters as it flows through the system. This includes resistance from ductwork, filters, grilles, and other components. Fans must overcome this pressure to maintain airflow, and higher static pressure requires more power.
Fan Laws
Fan laws describe the relationships between fan speed, airflow, pressure, and power:
- •Flow is proportional to speed (CFM ∝ RPM)
- •Pressure is proportional to speed squared (P ∝ RPM²)
- •Power is proportional to speed cubed (Power ∝ RPM³)
Efficiency
Fan efficiency is the ratio of useful air power output to mechanical power input. Higher efficiency means less energy consumption and lower operating costs. Modern fans can achieve efficiencies of 60-85% for centrifugal designs and 40-60% for axial designs.
Key Formulas
Air Power
P_air = Q × ΔP
Where Q is airflow (m³/s) and ΔP is pressure (Pa)
Shaft Power
P_shaft = P_air / η_fan
Where η_fan is fan efficiency (decimal)