Mechanical
Specific Fan Power Calculator
Calculate or estimate specific fan power from airflow, fan input power, pressure rise and efficiency.
Use this calculator for preliminary system fan power checks where either the design fan input powers are known, or fan power is to be estimated from system pressure and overall efficiency. It is intended for early-stage design checks and comparison of ventilation system performance.
Inputs
Result
Specific Fan Power
-
Enter values and click calculate.
Method
Specific fan power is calculated from total fan input power and system airflow:
SFP = P ÷ Q
Where fan power is not known, it can be estimated from airflow, total pressure and overall efficiency:
P = (Q × ΔP) ÷ η
- SFP = specific fan power
- P = total fan input power (W)
- Q = airflow rate (L/s or m³/s depending on expression)
- ΔP = total system pressure (Pa)
- η = overall fan system efficiency
- Calculated result = -
Reference
- This calculator evaluates specific fan power from either known fan electrical input power or an estimated power derived from airflow, pressure and overall efficiency.
- SFP is commonly used as a standardised measure of how much total fan power is required to move air through the connected system.
- Relevant guidance may include BS EN 16798-3, Approved Document L and CIBSE guidance relating to ventilation systems and energy performance.
- Where applicable, final design and compliance checks should align with the agreed project compliance route and installed system arrangement.
Design note: This calculator is an indicative design and checking tool only. Final compliance should be based on the actual installed system arrangement, design operating point, controls, component losses and the applicable project compliance route.