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CPU Cooler CFM Calculator

How to Calculate CPU Cooler CFM

To calculate the required CFM for a CPU cooler, you need to know the power consumption, fan power consumption, ambient temperature, and allowed CPU temperature. The formulas are:

Q = 0.09 P / ΔT (CMM)

Q = 3.16 P / ΔT (CFM)

Use the form above to input the values, and the calculator will provide the required airflow in both CMM and CFM.

Air Volume Calculation Method


1. Prerequisites

The following known conditions must first be understood:

  1. 1 calorie (cal) equals the amount of heat required to raise the temperature of 1g of water at 0℃ by 1℃.
  2. 1 watt of power operating for 1 second equals 1 joule (J).
  3. 1 calorie equals 4.2 joules.
  4. The specific heat at constant pressure (Cp) of air at 10mmAq = 0.24 (Kcal/Kg℃).
  5. Standard air conditions: temperature 20℃, atmospheric pressure 760mmHg, humidity 65%. At this state, the weight (also known as specific weight) of air per unit volume is 1200g/m³.
  6. CMM (Cubic Meter per Minute) and CFM (Cubic Feet per Minute) refer to the volume of air discharged per minute. The former's unit is m³/min, and the latter's is ft³/min. 1 CMM = 35.3 CFM.

2. Formula Derivation
  1. Given: Total Heat Output (H) = Specific Heat (Cp) × Weight (W) × Allowable Temperature Rise (△Tc).
    Since: Weight (W) = Volume per second × Density,
    i.e., W = (CMM / 60) × D.
    Substituting values: W = (CMM / 60) × 1200g/m³.
    Therefore: H = 0.24 × (Q / 60) × 1200g/m³ × △Tc.
  2. Electrical heat output: H = (P [power] × t [seconds]) / 4.2.
  3. Combining 1 and 2, we get:
    0.24 × (Q / 60) × 1200g/m³ × △Tc = (P × t) / 4.2.
    Solving for Q:
    Q = (P × 60) / (1200 × 4.2 × 0.24 × △Tc).
    Simplifying:
    Q = 0.05P / △Tc (CMM).
    Converting to CFM:
    Q = 0.05 × 35.3P / △Tc = 1.76P / △Tc (CFM).
  4. Converting to Fahrenheit temperature difference (1℃ = 1.8℉):
    Q = 0.05 × 1.8P / △Tf = 0.09P / △Tf (CMM).
    Q = 1.76 × 1.8P / △Tf = 3.16P / △Tf (CFM).
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