How to use the dew point calculator
Estimate dew point from air temperature and humidity. Enter air temperature, relative humidity in the fields above; the dew point is computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- T — Air temperature (°C)
- RH — Relative humidity (%)
Worked example
With air temperature = 25 °C, relative humidity = 60 %, the calculator gives dew point ≈ 16.69766 °C.
Frequently asked questions
What is the formula for the dew point calculation?
Dew point (°C) = 243.04 × (ln(RH / 100)+17.625 × T / (243.04+T)) / (17.625-ln(RH / 100)-17.625 × T / (243.04+T)). Here T is air temperature (°C), RH is relative humidity (%).
What inputs do I need for the dew point calculator?
You need air temperature in °C, relative humidity in %. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.