.dewpoint-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #fdfdfd;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}
.dewpoint-calculator-container h2 {
color: #2c3e50;
text-align: center;
margin-bottom: 25px;
font-size: 1.8em;
}
.dewpoint-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-direction: column;
}
.dewpoint-calculator-container label {
display: block;
margin-bottom: 8px;
color: #34495e;
font-weight: bold;
font-size: 1.05em;
}
.dewpoint-calculator-container input[type="number"],
.dewpoint-calculator-container select {
width: calc(100% – 22px);
padding: 12px;
border: 1px solid #ccc;
border-radius: 6px;
font-size: 1em;
box-sizing: border-box;
transition: border-color 0.3s ease;
}
.dewpoint-calculator-container input[type="number"]:focus,
.dewpoint-calculator-container select:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 5px rgba(0, 123, 255, 0.2);
}
.dewpoint-calculator-container .temp-input-group {
display: flex;
gap: 10px;
}
.dewpoint-calculator-container .temp-input-group input {
flex-grow: 1;
}
.dewpoint-calculator-container .temp-input-group select {
width: auto;
min-width: 100px;
}
.dewpoint-calculator-container button {
width: 100%;
padding: 14px;
background-color: #007bff;
color: white;
border: none;
border-radius: 6px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 20px;
}
.dewpoint-calculator-container button:hover {
background-color: #0056b3;
transform: translateY(-1px);
}
.dewpoint-calculator-container #result {
margin-top: 25px;
padding: 18px;
border: 1px solid #d4edda;
background-color: #e9f7ef;
border-radius: 8px;
font-size: 1.15em;
color: #155724;
text-align: center;
font-weight: bold;
}
.dewpoint-calculator-container #result p {
margin: 5px 0;
}
.dewpoint-calculator-container #result p:first-child {
margin-top: 0;
font-size: 1.2em;
color: #2c3e50;
}
.dewpoint-calculator-container .article-content {
margin-top: 40px;
line-height: 1.7;
color: #333;
font-size: 1.05em;
}
.dewpoint-calculator-container .article-content h3 {
color: #2c3e50;
margin-top: 30px;
margin-bottom: 15px;
font-size: 1.5em;
border-bottom: 2px solid #eee;
padding-bottom: 5px;
}
.dewpoint-calculator-container .article-content p {
margin-bottom: 15px;
}
.dewpoint-calculator-container .article-content ul {
list-style-type: disc;
margin-left: 20px;
margin-bottom: 15px;
}
.dewpoint-calculator-container .article-content li {
margin-bottom: 8px;
}
What is Dew Point?
The dew point is the temperature to which air must be cooled to become saturated with water vapor. At this temperature, water vapor condenses into liquid water (dew, fog, or clouds). It's a crucial indicator of atmospheric moisture content and is often considered a more accurate measure of how "humid" it feels than relative humidity alone.
Why is Dew Point Important?
Understanding the dew point has several practical applications:
- Human Comfort: A high dew point (above 65°F or 18°C) indicates very humid conditions, making it feel muggy and uncomfortable. Lower dew points (below 50°F or 10°C) suggest dry, comfortable air.
- Weather Forecasting: Meteorologists use dew point to predict fog, dew, and cloud formation. When the ambient temperature drops to meet the dew point, condensation occurs.
- Agriculture: Farmers monitor dew point to predict conditions favorable for crop diseases (which thrive in high humidity) or to plan irrigation.
- Industrial Processes: In many industries, controlling humidity is critical. For example, in manufacturing, painting, or storage, maintaining a specific dew point prevents corrosion, mold, or product damage.
- Aviation: Pilots need to be aware of dew point to assess the risk of carburetor icing or fog formation, which can affect visibility and engine performance.
How is Dew Point Calculated?
The dew point is not measured directly by a simple thermometer. Instead, it's derived from the ambient air temperature and relative humidity using specific psychrometric formulas. The calculator above uses a widely accepted approximation based on the Magnus formula, which relates temperature, relative humidity, and the saturation vapor pressure of water.
The core idea is that warmer air can hold more moisture than colder air. Relative humidity tells us how much moisture the air currently holds compared to its maximum capacity at that temperature. The dew point tells us the temperature at which the air would reach 100% relative humidity (saturation) if cooled without changing its moisture content.
Interpreting Dew Point Values:
- Below 50°F (10°C): Very dry and comfortable.
- 50-60°F (10-15°C): Comfortable, pleasant.
- 60-65°F (15-18°C): Becoming muggy, noticeable humidity.
- 65-70°F (18-21°C): Very humid, uncomfortable for many.
- Above 70°F (21°C): Oppressive, tropical humidity.
Example Calculation:
Let's say the ambient temperature is 25°C (77°F) and the relative humidity is 60%. Using the calculator:
- Input Temperature: 25 °C
- Input Relative Humidity: 60 %
- The calculated dew point would be approximately 16.7°C (62.1°F).
This indicates that if the air cools to 16.7°C, water vapor will begin to condense. A dew point of 16.7°C suggests moderately humid conditions, which might feel a bit sticky but generally tolerable for most people.
function calculateDewPoint() {
var tempInput = document.getElementById("ambientTemperature").value;
var rhInput = document.getElementById("relativeHumidity").value;
var tempUnit = document.getElementById("temperatureUnit").value;
var T = parseFloat(tempInput);
var RH = parseFloat(rhInput);
if (isNaN(T) || isNaN(RH)) {
document.getElementById("result").innerHTML = "Please enter valid numbers for temperature and relative humidity.";
return;
}
if (RH 100) {
document.getElementById("result").innerHTML = "Relative Humidity must be between 0 and 100%.";
return;
}
var T_celsius;
if (tempUnit === "fahrenheit") {
T_celsius = (T – 32) * 5 / 9;
} else { // celsius
T_celsius = T;
}
// Magnus formula constants (commonly used approximation)
var a = 17.27;
var b = 237.7;
// Calculate gamma
var gamma = (a * T_celsius) / (b + T_celsius) + Math.log(RH / 100);
// Calculate dew point in Celsius
var Td_celsius = (b * gamma) / (a – gamma);
// Convert dew point to Fahrenheit
var Td_fahrenheit = (Td_celsius * 9 / 5) + 32;
document.getElementById("result").innerHTML =
"
" +
"" + Td_celsius.toFixed(2) + " °C" +
"" + Td_fahrenheit.toFixed(2) + " °F";
}