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LoadCairn / Cooling airflow

Cooling airflow calculator

Estimate sensible cooling airflow from a heat load and temperature rise. The calculation runs in your browser and shows the coefficient and assumptions behind the result.

Inputs

Illustrative example · editable

Starting values: 10,000 BTU/hr sensible heat and a 20°F temperature rise. These are examples, not site conditions or recommended design values.

Enter sensible heat only. This estimate does not include latent heat from moisture. Example: 10000.

Use the temperature difference across the cooling air stream; the value must be above zero. Example: 20.

Live estimate

Rounded to the nearest whole CFM; the calculation retains its precision.

Estimated airflow
463CFM

Before whole-CFM rounding (shown to 3 decimals): 462.963 CFM.

Inputs used

Sensible heat load
10000 BTU/hr
Temperature rise
20 °F

Formula and calculation trace

CFM = sensible heat load (BTU/hr) ÷ (1.08 × temperature rise (°F))

10000 ÷ (1.08 × 20) = 462.963 CFM

Assumptions and source

  • The entered load is sensible heat only. Latent load from moisture is not calculated.
  • The 1.08 BTU/(hr·CFM·°F) coefficient is a simplified dry-air sensible-heat factor at standard air conditions. ASHRAE shows the factor varies with humidity ratio (1.08 at W = 0; 1.10 at W = 0.01) and notes altitude correction for other elevations; this estimate applies no air-state or elevation correction.
  • Reference: ASHRAE Handbook, Chapter 18 — Nonresidential Cooling and Heating Load Calculations. The source describes calculation methods and assumptions; it does not endorse this calculator.

Planning estimate only. This is not an engineered airflow design or an equipment rating.