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Atmosphere & Weather
Estimated Cloud Base Calculator
Estimate convective cloud base from surface temperature/dew-point spread.
°C
°C
Estimated base—
Temperature spread—
Approx. base MSL if field elevation supplied below—
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A 10°C temperature–dew point spread
A surface temperature of 25°C and dew point of 15°C gives a 10°C spread. The tool uses 10 / 2.444444 × 1,000 ≈ 4,091 ft AGL.
The often-used 400 ft per °C shortcut gives 4,000 ft. Both are rough convective estimates, not a reported ceiling; do not use them to select an IFR minimum or infer VFR conditions.
Formula and method
The convective cloud-base shortcut uses surface temperature/dew-point spread and a standard training approximation; it is not a ceiling forecast.