Relative Humidity Calculator
Find relative humidity from temperature and dewpoint, see the temperature-dewpoint spread, and check carburetor icing risk. A small spread means the air is near saturation — more likely fog, low cloud, and induction icing.
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Carburetor Icing Risk (FAA AC 61-23C)
| Risk Level | Condition | Meaning |
|---|---|---|
| Serious (Red) | Temp 20–70°F, spread ≤ 5°F | Serious carburetor icing risk at any power setting |
| Moderate (Amber) | Temp 20–70°F, spread 5–15°F | Moderate carburetor icing risk at descent/low power |
| Moderate (Yellow) | Temp 20–70°F, spread 15–30°F | Moderate carburetor icing risk at cruise power |
| Low (Green) | All other conditions | Low carburetor icing risk |
This indicator is based on the FAA carburetor icing probability chart (AC 61-23C). It applies to carbureted engines only. Fuel-injected engines are not susceptible to carburetor ice but may experience induction icing under certain conditions. Always follow your aircraft’s POH for carburetor heat procedures.
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Frequently Asked Questions
This calculator is for educational and planning purposes only. Always refer to your aircraft's POH/AFM, current NOTAMs, and official weather briefings. No calculator is a substitute for pilot-in-command judgment or CFI guidance.
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