Series Fans Pressure Calculator
Combined static pressure of identical fans in series.
Enter your values
ⓘ Live results
Results
- Ideal combined pressure
- 3 in wc
- Realistic combined pressure
- 2.7 in wc
- Loss to interaction
- 0.3 in wc
Quick answer
Ideal series pressure is the sum of each fan's pressure at a given flow, but real systems typically achieve 85-95% of that sum due to inlet turbulence between stages.
SP_combined = n x SP_single x derate
How to use the Series Fans Pressure Calculator
- 1Enter the number of identical fans staged in series and each one's pressure at the shared flow rate.
- 2Apply an interaction derate for turbulence between stages (typically 85-95%).
- 3Use the realistic combined pressure to check the system can be overcome.
Worked example
Using the values the calculator loads with:
Inputs
- Number of fans in series2
- Pressure per fan alone1.5 in wc
- Interaction derate90 %
Results
- Ideal combined pressure3 in wc
- Realistic combined pressure2.7 in wc
- Loss to interaction0.3 in wc
Frequently asked questions
Why stage fans in series instead of one bigger fan?
Series staging (like inline duct boosters) can be a simpler retrofit than replacing a single fan with a larger unit.
Does spacing between fans matter?
Yes — more distance between stages reduces turbulent interaction and improves the combined pressure.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.