Enclosure Airflow Calculator (CFM)
Fan airflow needed for your heat load and allowed air rise — the 1.76·P/ΔT rule both directions, with back-pressure notes.
This gives the BULK air rise — hot components still sit above the LOCAL air temperature, so add their own θ rise on top. Fans deliver only 40–60 % of their free-air CFM once filters, grilles and back-pressure bite (hence the ÷2 hint). At altitude, thinner air cools less: derate ~10 % per 1000 m. Place intake low/cool side, exhaust high/hot side to recruit natural convection.
Enclosure Airflow Calculator computes the fan airflow (CFM) an enclosure needs, or the air temperature rise it will see — free, instant and private in your browser. Cabinet, server-closet and equipment-box designers sizing fans and vents use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Enclosure Airflow Calculator (CFM)
Enclosure Airflow Calculator computes the fan airflow (CFM) an enclosure needs, or the air temperature rise it will see using the standard engineering relation: CFM ≈ 1.76·P(W)/ΔT(°C) — from the energy balance P = ρ·cp·Q·ΔT. Worked live: 120 W of electronics with a 10 °C allowed air rise needs ~21 CFM of real through-flow. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Enclosure Airflow Calculator (CFM)
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Enclosure Airflow Calculator (CFM)?
- ✓Implements the real formula — CFM ≈ 1.76·P(W)/ΔT(°C) — from the energy balance P = ρ·cp·Q·ΔT — with the substitution shown, not a black box
- ✓Built for cabinet, server-closet and equipment-box designers sizing fans and vents
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate enclosure airflow?+
The fan airflow (CFM) an enclosure needs, or the air temperature rise it will see follows CFM ≈ 1.76·P(W)/ΔT(°C) — from the energy balance P = ρ·cp·Q·ΔT. For example, 120 W of electronics with a 10 °C allowed air rise needs ~21 CFM of real through-flow. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why does my fan's rated CFM not match reality?+
Ratings are free-air, zero back-pressure. Filters, grilles and packed boards typically cut delivered flow to 40–60 % — the standard practice is to halve the nameplate CFM in this calculation, or read the fan's P-Q curve against your enclosure's impedance.
Intake at the bottom or exhaust at the top?+
Both, diagonally: cool intake low on one side, exhaust high on the opposite, so forced flow and natural convection cooperate and no stagnant pocket forms. Slight positive pressure (intake fan + filtered) keeps dust out better than negative.
Is the Enclosure Airflow Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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