Free tools for fan engineers
The calculations we build into selection software every day, opened up as standalone calculators. No sign-up, no email wall, no watermark on the result — every tool states the standard it implements and links to the primary source, so you can check the arithmetic yourself.
ErP 2026 compliance calculator
Check a fan against Regulation (EU) 2024/1834, in force since 24 July 2026. Required minimum efficiency, the N grade applied, correction factors and the maximum input power that still complies.
EU 2024/1834 · Live
Fan Energy Index calculator
FEI at any duty point per ANSI/AMCA 208-18, with the full reference fan chain and a check against the ASHRAE 90.1 and IECC thresholds.
ANSI/AMCA 208-18 · Live
Fan power calculator
Electrical input power from airflow, pressure and overall efficiency, plus annual energy consumption, annual energy cost and Specific Fan Power (SFP).
SFP · Live
Fan acoustic calculator (VDI 3731)
Octave-band sound power from the aerodynamic duty point and fan geometry, plus the sound pressure level at a distance — inlet and outlet, A-weighted.
VDI 3731 · Live
Sound source summation calculator
Combine multiple noise sources into the total sound pressure level at a receiver — place them on a room plan or enter distance and directivity manually.
Logarithmic sum · Live
Fan operating point calculator
One duty point, every number that matters: velocities, density, motor load and efficiency, static/total/impeller efficiency, torque, SFP, FEI and VDI 3731 sound power.
All-in-one · Live
Duct network configurator
Build a branching duct run — ducts, reducers, elbows, tees, dampers and louvers — and get velocity, Reynolds number and total pressure loss down every path, per Darcy-Weisbach + Colebrook-White.
Darcy-Weisbach · Live
Duct sizing calculator
Size a round and a rectangular duct to the same target velocity or friction rate, then see both shapes drawn overlaid, to scale.
Round & rectangular · Live
Duct pressure drop calculator
Airflow, size and length in — velocity and pressure loss out, for one round or rectangular duct run. The quick single-duct version of the tools around it.
Darcy-Weisbach · Live
Motor efficiency calculator
Nominal efficiency for IE1–IE5 by rated power and pole count, per IEC 60034-30-1, plus input power and losses.
IEC 60034-30-1 · Live
EC vs AC motor payback calculator
Energy savings and simple payback for switching to an EC motor, from IE-class efficiency, energy price and upgrade cost.
Simple payback · Live
Belt drive & pulley ratio calculator
Pulley ratio, belt length, wrap angle, torque and AMCA 203 drive efficiency, with a to-scale drive diagram.
AMCA 203 · Live
Motor starting calculator
Simulates speed, line current, torque and winding temperature over time for DOL, Star-Delta, Autotransformer, Soft Starter and VFD starting.
Torque-slip simulation · Live
Fan array calculator
Ideal array performance (AMCA 270) plus the AMCA 201 System Effect Factor from wall clearance, partitions and fan-to-fan spacing — with a live layout diagram.
AMCA 201 & 270 · Live
Air compressibility calculator
The AMCA 210 compressibility coefficient K<sub>p</sub> and corrected fan output power — the correction that starts to matter above 2.5 kPa.
AMCA 210 §7.8 · Live
Splitter silencer designer
Pressure loss and self-generated flow noise through a rectangular splitter (baffle) silencer, via VDI 2081 Blatt 1's own correlations — verified against the standard's published worked example.
VDI 2081 Blatt 1 · Live
Circular silencer designer
Airway velocity, pressure loss and an ASHRAE-based insertion-loss estimate for a round (tube) duct silencer, with an optional central pod for larger sizes.
General engineering model · Live
HVAC unit converter
Flow, pressure, power, SFP, velocity, rotation, temperature, density, dimensions and area — metric and imperial, all on one page.
19 categories · Live
Fan laws calculator
Scale flow, pressure and power between two operating conditions using the fan affinity laws — speed, diameter and density.
Affinity laws · Live
Air density calculator
Correct a duty point for temperature, altitude and humidity — actual density and the ratio versus standard conditions.
Barometric formula · Live
Mollier (h-x) diagram calculator
Humidity ratio, enthalpy, dew point and wet-bulb temperature from dry-bulb temperature, relative humidity and altitude.
ASHRAE / WMO psychrometrics · Live
Condensation risk calculator
Dew point vs. surface temperature for a duct or pipe, plus the minimum insulation thickness needed to stay above it.
Dew point + heat transfer · Live
U-value (thermal transmittance) calculator
Build up a wall, roof or floor from its actual material layers and get the U-value per EN ISO 6946 — cross-section drawing, resistance breakdown, add as many layers as needed.
EN ISO 6946 · Live
Material quantity calculator
Give a wall, roof or floor construction's area and get the volume and mass of each material — a bill of quantities for procurement or structural loading checks. Shares the U-Value calculator's material list, and can import its constructions directly.
Volume · Mass · Live
Heat loss / heating load calculator
Room heat loss from dimensions, design temperatures and U-values for walls, windows, doors, ceiling and floor — typical construction presets or your own values — plus ventilation and infiltration. Required heating load, broken down by element.
U · A · ΔT · Live
Cooling load calculator
Room cooling load from envelope U-values plus solar gain by window orientation and glazing g-value, internal gains and ventilation. Required cooling capacity, broken down by source. Shares the Heat Loss calculator's U-value tables.
Transmission + solar + internal · Live
Heater/cooler coil designer
Build a fin-tube coil from face size, rows, tube and fin data — tube count, total length, mass, water volume and heat-transfer area, with a dimensioned drawing and a 3D model.
Fin-tube geometry · 3D model · Live
Heat pump sizing calculator
Balance point between building heat loss and heat pump capacity, backup heater sizing, and capacity/COP curves — from your datasheet's own points.
Balance point · Live
Heat recovery efficiency calculator
EN 308 temperature efficiency and recovered heat power for an air-to-air heat recovery device — from measured data, or predicted from exchanger type.
EN 308 · Live
Water flow power calculator
Solve capacity (kW), water flow rate or ΔT from the other two, using real water density and specific heat at your system's mean temperature.
Q = flow · ρ · c<sub>p</sub> · ΔT · Live
CHW pipe size calculator
Size a chilled/heating water pipe from a target velocity, or check an existing pipe's velocity and pressure drop.
Darcy-Weisbach · Live
Gas air heater sizing calculator
Size a gas-fired air heater from airflow and target temperature rise — heat output, gas consumption, modulation range and turndown ratio.
Q = ṁ·c<sub>p</sub>·ΔT · Live
Ecodesign compliance checker
Check air heaters, heat pumps, chillers, air conditioners and process chillers against Regulation (EU) 2016/2281's minimum efficiency and NO<sub>x</sub> thresholds.
EU 2016/2281 · Live
Building airflow designer
Add every room by occupancy, residential, public/industrial or kitchen-hood method, then see the whole building's supply vs exhaust balance and pressurization risk.
Supply / exhaust balance · Live
Refrigerant pipe pressure drop calculator
Velocity, Reynolds number and pressure loss for a single-phase suction, discharge or liquid line, with an oil-return velocity guideline check.
Darcy-Weisbach · Live
Refrigerant cooling capacity calculator
Solve cooling capacity, refrigerant mass flow or evaporator Δh from the other two — an exact energy balance, Q = mass flow × Δh.
Q = ṁ · Δh · Live
COP / EER calculator
Solve capacity, power input or COP from the other two, convert to EER and kW/ton, and compare against the theoretical Carnot ceiling.
Carnot ceiling · Live
Compressor power calculator
Ideal-gas isentropic compression power from suction/discharge pressure and flow, with isentropic and motor efficiency stacked to shaft and electrical power.
Isentropic compression · Live
Ventilation airflow calculator
Required air quantity by room type — offices, residential, public and industrial buildings — plus commercial kitchen hood extraction design per PN-EN 16282-1.
PN-83/B-03430 · PN-EN 16798-1 · Live
Air changes (ACH) calculator
Room volume × air-change rate = required airflow — pick a room type from an international or Poland-specific reference table, or enter your own ACH.
IMC 403.3.1.1 · ASHRAE 170 · Live
Electricity carbon footprint calculator
Annual and lifetime CO2 for any electrical load, from power, operating hours and grid carbon intensity for 55+ countries.
Ember grid data · Live
Primary energy & CO2 calculator
Annual final energy (kWh/yr) into primary energy and CO2 emissions — gas, oil, coal, biomass, district heating, or grid electricity by country with real Ember/OWID data.
Final × PEF · Live
System Effect Factor calculator (AMCA 201)
Outlet/inlet ducts, elbows, dampers, obstructions and enclosure effects for centrifugal and axial fans — full AMCA 201-02 coverage.
AMCA 201-02 · Live
Fan balance & vibration severity calculator (AMCA 204)
Balance category, required balance grade, permissible unbalance and vibration velocity limits, with a resonance/dynamic amplification chart.
AMCA 204-05 · Live
Fan Efficiency Grade (FEG) calculator (AMCA 205)
Impeller diameter and peak efficiency to FEG classification, with a diameter-vs- efficiency grade curve chart.
AMCA 205-10 · Live
Centrifugal fan designer
Check a candidate impeller against a duty point via the Euler equation and Stanitz slip factor, size a matching volute casing, and select a motor with IEC 60034-30-1 efficiency.
Euler equation · LiveWhy we publish these
CloudAir builds fan selection software for manufacturers. Every program we deliver contains the same core arithmetic: efficiency and compliance checks, fan laws, acoustics, density corrections. None of that is proprietary — it comes from published standards and it should be easy to check.
So we opened the calculations up. Each tool implements one standard, states which one, links to the primary text, and produces a result you can share as a link. If a number here disagrees with your own sheet, the formulas are written out on the page so you can find out which of us is wrong.
What these tools deliberately do not do is select a fan. They evaluate one duty point against one criterion. The moment you need to run the same check across four hundred catalogue items, generate declared values for every published operating point and hand a customer a selection card in PDF — that is a selection program, and that is what we build.
Standards implemented
| Tool | Standard or regulation | Region |
|---|---|---|
| ErP 2026 compliance | Regulation (EU) 2024/1834, amended by (EU) 2025/2481 | European Union |
| Fan Energy Index | ANSI/AMCA 208-18; ASHRAE 90.1-2019, IECC 2021 | United States |
Want a calculator we have not built yet? Tell us which one and what it has to handle — we add tools based on what people actually ask for. Send us a note →