Interactive Calculator · 2026
Blower Size Calculator
Size the aeration blower for a sewage treatment plant. Enter the air flow and discharge head, and get the shaft power in kW, the motor rating in HP and a recommended standard motor — the numbers every blower specification starts from.
Shaft power → recommended motor rating (kW)
Blower duty
Free air delivery required at the diffusers.
Diffuser submergence + pipe and header losses.
Overall wire-to-air efficiency of the blower package — positive-displacement units typically sit at 55–65%.
Shaft power vs recommended motor
Both shown in kW so you can see the ≈15% margin built into the standard motor rating.
The blower absorbs about 6.81 kW at the shaft. A driving motor is never picked at exactly that figure — you add a service margin and round up to the next standard frame.
Here that lands on a 11 HP motor (≈8.2 kW), leaving headroom for start-up, fouling and warm-day air density.
How this is calculated
- Air flow = 5 m³/min ÷ 60 = 0.08 m³/s.
- Pressure rise = 5 m × 9,810 Pa/m = 49,050 Pa.
- Shaft power = (air flow × pressure) ÷ efficiency ÷ 1,000 = (0.08 × 49,050) ÷ 0.60 ÷ 1,000 = 6.81 kW.
- Motor HP = 6.81 kW × 1.341 = 9.14 HP.
- Recommended motor = ceil(9.14 HP × 1.15) = 11 HP.
Indicative sizing for concept planning. A detailed design must also fix air temperature, altitude, diffuser type and control turndown — confirm with a qualified consultant before procurement.
Related Guides — Deep-dive reading
Aeration Design Principles for STPs: Oxygen Demand, Diffusers & Blower Sizing
How engineers actually size the aeration system at the heart of a sewage treatment plant — from oxygen demand and alpha/beta factors to SOTE, fine versus coarse bubble diffusers, blower selection and the energy bill that follows for decades.
Sewage Treatment PlantsSTP for Shopping Malls: Mixed Loads, Big Reuse
Why a mall's wastewater is unlike any other building's — a punishing mix of food-court grease, washroom peaks and huge cooling-tower thirst — and how to size, site and choose an STP that turns all of it back into usable water in the basement.
Sewage Treatment PlantsEnergy-Efficient STP Design: How to Build a Plant That Sips Power
Aeration eats 50-70% of an STP's electricity bill. This guide shows how right-sized blowers, fine-bubble diffusers, DO control with VFDs, gravity flow and the right technology cut running cost for the life of the plant.
Sewage Treatment PlantsRelated Tools — You may also find these useful
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