# Dew Point Calculator

URL: https://speedycalculator.com/calculators/physics/dew-point/
Last updated: 2026-10-25

> The dew point calculator finds the temperature at which air becomes saturated and dew or fog forms, from air temperature and relative humidity, using the Magnus formula.

## Inputs

- Air temperature (°C, °F, K)
- Relative humidity (%)

## Results

- Dew point

## Formula

```
γ = ln(RH ÷ 100) + b T ÷ (c + T)
Dew point = c γ ÷ (b − γ),  b = 17.62, c = 243.12 °C
```

## Explanation

Dew point is a better comfort guide than relative humidity: above about 20 °C most people feel muggy.

### How to use the Dew Point Calculator

- **Air temperature**
- **Relative humidity**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The Magnus approximation relates saturation vapour pressure to temperature.

### Inputs explained

FieldWhat to enterAir temperatureUnits: °C, °F, KRelative humidityIn %

### Example values

How the main result changes when **Air temperature** changes and everything else stays at the example values above:

Air temperature (°C)Dew point (°C)12.54.918.7510.82516.731.2522.637.528.45040.1

## Worked example

Inputs — Air temperature: 25 °C; Relative humidity: 60 %.

Results — **Dew point = 16.7 °C**.

## FAQ

**Why does dew form at night?**
Surfaces cool below the dew point and water condenses on them.

**Can dew point exceed air temperature?**
No; when they are equal, humidity is 100%.

**What formula does the Dew Point Calculator use?**
γ = ln(RH ÷ 100) + b T ÷ (c + T).