Dew Point Calculator
Calculate Dew Point Temperature & Humidity - Condensation Temperature & Moisture Assessment
💧 Pro Tips for Dew Point Calculations:
Dew point = saturation temperature (moisture condenses). Magnus formula provides accurate approximation. Below dew point: condensation/frost forms. Higher dew point = more moisture. Comfort: 60-70°F optimal. 80°F+ dew point oppressive/dangerous. Temperature, humidity, and dew point interdependent.
Calculate Dew Point from Temperature & Humidity
✅ Dew Point Calculation Results:
Calculate Humidity from Temperature & Dew Point
✅ Humidity Calculation Results:
Absolute Humidity Calculator
✅ Absolute Humidity Results:
Dew Point Reference & Comfort Guidelines
Dew Point & Comfort Levels:
| Dew Point (°F) | Dew Point (°C) | Comfort Level | Description |
|---|---|---|---|
| Below 50°F | Below 10°C | Very Dry | Dry skin/nasal passages. Risk of skin cracking. |
| 50-60°F | 10-15°C | Dry | Comfortable for most people. Slightly dry. |
| 60-70°F | 15-21°C | Comfortable | Optimal indoor humidity. Most people comfortable. |
| 70-75°F | 21-24°C | Humid | Noticeably humid. Perspiration slower to evaporate. |
| 75-80°F | 24-27°C | Very Humid | Very humid/uncomfortable. Condensation likely. |
| Above 80°F | Above 27°C | Oppressive | Dangerous heat perception. Heat illness risk during hot weather. |
Magnus Formula Coefficients:
Magnus approximation (accurate -40 to 50°C):
Td = T - ((100-RH)/5)
More accurate Magnus formula:
α = ((a × T)/(b + T)) + ln(RH/100)
Td = (b × α)/(a - α)
Where: a = 17.27, b = 237.7
Td = T - ((100-RH)/5)
More accurate Magnus formula:
α = ((a × T)/(b + T)) + ln(RH/100)
Td = (b × α)/(a - α)
Where: a = 17.27, b = 237.7
Temperature Unit Conversions:
| From | To | Formula | Example |
|---|---|---|---|
| Celsius | Fahrenheit | (C × 9/5) + 32 | 20°C = 68°F |
| Fahrenheit | Celsius | (F - 32) × 5/9 | 68°F = 20°C |
| Celsius | Kelvin | C + 273.15 | 20°C = 293.15K |
💧 Understanding Dew Point & Humidity
What is Dew Point?:
Dew point: temperature at which air becomes saturated with moisture. When air cools to dew point, water vapor condenses to dew/frost. Direct indicator of atmospheric moisture content. Independent of temperature changes (unlike relative humidity). Higher dew point = more moisture present.
Relative vs. Absolute Humidity:- Relative Humidity: Percentage of maximum moisture air holds at current temperature. Changes with temperature. Same moisture content: different RH at different temperatures.
- Absolute Humidity: Mass of water vapor per unit volume (g/m³). Independent of temperature. Same absolute humidity = same moisture content regardless of temperature.
- Dew Point: Temperature at saturation. Direct moisture indicator. Remains constant despite temperature/pressure changes (at fixed moisture content).
- Condensation Formation: When surface cools below dew point, water vapor condenses. Windows fog when interior dew point exceeds cold glass temperature.
- Weather Prediction: High dew point indicates moisture-laden air. Predictor of rain/frost formation. Meteorologists use dew point for analysis.
- Aviation Safety: Dew point depression (temp minus dew point) used to predict carburetor icing. Fuel system icing conditions assessed via dew point.
- Industrial Applications: Compressed air drying monitored via dew point. Electronics manufacturing requires low dew point (<-40°C). HVAC systems designed for target dew points.
- Body Cooling: High dew point reduces evaporative cooling effectiveness. Perspiration cannot evaporate efficiently. Body retains heat, feels hotter.
- Perception Variation: Individual perception varies. Acclimatization to high dew points possible. Generally, dew points above 70°F perceived as uncomfortable.
- Health Considerations: Very low dew point (<40°F) causes dry skin, nasal irritation. High dew point (>75°F) during hot weather increases heat illness risk.
- Optimal Indoor Conditions: OSHA recommends 68-76°F temperature, 20-60% RH (approximately 35-60°F dew point). Comfort varies with activity level and clothing.
❓ Frequently Asked Questions
Why is dew point important for weather forecasting?
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Dew point directly indicates moisture. High dew point (>65°F) with temperature drop predicts rain/fog. Frost formation risk when temperature drops toward/below dew point. Meteorologists use dew point for severe weather prediction. Provides more intuitive weather assessment than relative humidity.
Can dew point change without temperature changing?
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Yes. Dew point changes when atmospheric moisture changes. Adding moisture (evaporation) raises dew point. Removing moisture (condensation) lowers dew point. Temperature can remain constant while dew point varies. Dew point depression (temp minus dew point) changes despite steady temperature.
Why is frost called "dew" if it forms from dew point?
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Frost forms when dew point is below freezing (below 32°F/0°C). Water vapor converts directly to ice crystals (deposition, no liquid phase). Dew forms at dew point above freezing (liquid condensation). Both form at dew point saturation, just different phase transitions based on temperature.
How does altitude affect dew point?
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Dew point slightly decreases with altitude (lower atmospheric pressure). Effect minor for typical elevations (<10,000 feet). Relative humidity increases at altitude (cooler temperatures). Actual moisture content (absolute humidity) decreases significantly with altitude.
Is there a maximum dew point value?
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Theoretically no absolute maximum, practically limited by temperature. Dew point cannot exceed air temperature (at 100% RH they're equal). Highest observed dew points: around 80-85°F in humid tropical regions. Higher dew points possible but rare/extreme conditions.
How does dew point affect athletic performance?
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High dew point (>65°F) significantly impairs performance. Reduced evaporative cooling prevents temperature regulation. Body overheats during exertion. Athletes dehydrate faster. Low dew point also problematic (very dry conditions cause dehydration faster). Optimal: dew point 55-70°F depending on activity intensity/duration.
Why do weather services report dew point?
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Dew point directly indicates comfort and precipitation potential. More intuitive than relative humidity (independent of temperature). Predicts frost/fog formation. Indicates moisture availability for storms. Used for heat index calculation. Helps people understand weather impact on activities/health.
Can I measure dew point with ordinary instruments?
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Direct measurement requires dew point meter (psychrometer). Calculate from temperature + humidity using calculator. Sling psychrometer: two thermometers (dry/wet bulb). Comparison: dry bulb temperature vs. psychrometer reading gives humidity/dew point. Digital hygrometers measure humidity for dew point calculation.