Cloud Base Calculator
Estimate cloud base AGL from temperature and dew point
How to Use This Calculator
1
Enter Air Temperature
Provide ambient temperature in °C.
2
Enter Dew Point
Provide dew point temperature in °C.
3
Calculate
Review cloud base height in feet and meters AGL.
Formula
Base(ft) ≈ (T − Td) · 125
Base(m) ≈ (T − Td) · 400
Where: T = temperature (°C), Td = dew point (°C)
Note: Rule-of-thumb for convective cloud base; local conditions vary.
About Cloud Base
Cloud base is the altitude where air becomes saturated and condensation begins. It is closely related to the temperature–dew point spread and vertical mixing.
Use Cases
- Aviation: VFR ceiling planning
- Meteorology: Convective cloud and thunderstorm assessment
- Outdoor planning: Anticipating low ceilings and fog
Frequently Asked Questions
How accurate is this estimate?
It is a rule of thumb; real cloud bases depend on lapse rates and mixing depth.
What if dew point equals temperature?
Then spread is zero, implying cloud or fog at the surface.