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Fan Engineering Calculators & Tools

Every calculation an HVAC, refrigeration, data-center or OEM engineer runs when sizing, selecting or troubleshooting a fan — airflow (CFM / m³/h), static pressure, fan laws, altitude derating, motor amps, bearing life, noise and more. Built and maintained by LONGWELL's fan engineers. Free, no signup, formulas shown on every page.

Airflow & Ventilation Sizing

How much air a room, process or enclosure needs.

💨CFM Calculator (Air Changes per Hour)Airflow (CFM / m³/h) a room needs by air changes per hour — 60+ space types.🔥Heat Load & Enclosure Cooling Airflow CalculatorCFM / m³/h to remove a heat load (W or kW) at an allowed temperature rise — cabinets, racks, inverters.❄️AC Size & Cooling Load Calculator (BTU / Tons / kW)Quick cooling load for a room or small building from area, climate, sun, occupants and equipment — and the supply airflow it implies.🍳Range Hood & Kitchen Exhaust CFM CalculatorRange hood and commercial kitchen hood exhaust airflow by hood length, cooking duty and hood type — plus make-up air.🏠Whole House Fan Sizing & Attic Fan CalculatorCFM for a whole-house fan (by climate and air changes) and for attic exhaust (by attic area), with vent-opening and window-opening checks.🚪Air Curtain Sizing CalculatorDischarge velocity, airflow and power for an air curtain by door height, width, wind and temperature difference.🪚Dust Collection CFM & Duct Velocity CalculatorCFM per machine, duct size for transport velocity, static pressure of the run and collector size for a workshop.🌱Grow Tent Fan Size Calculator (CFM & Carbon Filter)Inline exhaust fan CFM for a grow tent or grow room, with carbon-filter, duct, light-heat and CO₂ adjustments.

Pressure, Ducts & Units

Static pressure, duct losses and unit conversion.

🔁CFM to m³/h Converter (Airflow, Pressure & Velocity Units)CFM ↔ m³/h ↔ L/s ↔ m³/s, Pa ↔ in. w.g. ↔ mm H₂O, fpm ↔ m/s, plus velocity × area → airflow.🏔️Air Density Calculator (Altitude & Temperature) — Fan DeratingDensity at any altitude/temperature and how much to derate fan pressure, power and cooling.🧭Duct Size & Static Pressure CalculatorFriction loss, fittings and component pressure drop for a duct run — the static pressure your fan must overcome.🌡️BTU to kW, Tons & kcal/h ConverterConvert cooling/heating capacity between BTU/h, kW, tons of refrigeration, kcal/h and HP — and into airflow at a ΔT.

Fan Laws, Energy & Payback

Speed changes, electricity cost and ROI.

📐Fan Affinity Laws CalculatorNew airflow, pressure and power when you change fan speed, diameter or air density.💰VFD / Fan Speed Energy Savings CalculatorkWh, cost, CO₂ and payback from running a fan slower (VSD / EC control) instead of full speed.🔌Fan Power Consumption & Electricity Cost CalculatorHow much a fan costs to run per day, month and year from its watts, hours and tariff — and how two fans compare.♻️EC vs AC Energy Savings & ROI CalculatorAnnual kWh, cost, CO₂ and payback of replacing AC fans with EC fans.🧾Fan Total Cost of Ownership (TCO) CalculatorLifetime cost of two fan options: purchase price, energy, replacements, maintenance and downtime — side by side.

Motors, Electrical & Selection

Shaft power, amps, capacitors, fan type.

⚡Fan Motor Amps & Power Calculator (kW, HP, FLA)Shaft power from airflow × pressure, motor kW/HP to specify, and full-load amps by voltage and phase.📊Fan Efficiency Calculator (Static, Total & Wire-to-Air)Fan static/total efficiency and wire-to-air efficiency from airflow, pressure and measured power — with an FEI-style benchmark.🔋Fan Motor Capacitor Calculator (µF & Voltage)Run-capacitor µF and voltage for PSC / capacitor-run fan motors, from motor power or from measured values.🎯Fan Specific Speed & Type SelectorCalculate specific speed from airflow, pressure and rpm — and learn which fan type (axial, mixed, backward/forward-curved) fits.🔍EC Fan Selection CalculatorMatch airflow, static pressure, voltage and application to a Longwell EC fan size.📋ErP 2026 Fan Efficiency CalculatorMinimum threshold ηmin and corrected efficiency η per (EU) 2024/1834, with pass/fail verdict.

Noise, Vibration & Reliability

dB, blade-pass frequency, bearing life, redundancy.

🔇Fan Noise & Decibel (dB) CalculatorCombine several fans, convert sound power to pressure at a distance, and see the dB change from a speed change.🎵Blade Pass Frequency & Tip Speed CalculatorBPF tone (Hz), harmonics, tip speed and Mach number from blade count, rpm and diameter.⏳MTBF & L10 Bearing Life Calculator for FansExpected fan life in hours and years from the datasheet L10, operating temperature, speed and duty.🧱Fan Wall & N+1 Redundancy CalculatorHow many fans for a fan array, what happens when one fails, spare count and energy at part load.

Purchasing & Logistics

Container loading and sourcing helpers.

🚢CBM & Container Loading Calculator (20GP / 40HQ)How many cartons or pallets of fans fit in a container, by carton size and weight — with CBM, utilisation and weight limits.🧮Landed Cost Calculator (Import Duty, VAT & Freight)FOB price → ocean freight, insurance, duty (HS 8414), VAT, port & brokerage → true landed cost per unit.🌍Voltage, Frequency & Certification by Country (Fan Export Checker)Mains voltage, 50/60 Hz, plug type and mandatory marks (UL, CE, UKCA, CCC, KC, BIS…) for 40 markets — and whether your fan spec fits.

Why engineers use these tools

Most fan sizing mistakes come from three places: guessing the airflow, ignoring static pressure, and forgetting that air gets thinner with altitude and heat. These calculators walk the same path a Longwell application engineer follows — establish the duty point (airflow + pressure), correct it for the real installation, then check power, noise and life. Each tool shows its formula and typical reference values so you can check the result by hand or cite it in a report.

Results can be shared by link, copied as text, and referenced in your own articles. If you are specifying a fan, send the output to sales@longwellfans.com and we will match it to a catalog fan or quote a custom one.

Turn a calculation into a fan

3,800+ EC / AC / DC axial, centrifugal, cross-flow and duct fans. Catalog selection or full custom OEM development.

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