Cloud Base Calculator
Use our cloud base calculator to estimate cloud base altitude (ft) from temperature, dew point, and elevation. Includes the cloud base formula used in aviation, how to calculate cloud base from dew point spread, and a quick chart.
What Is Cloud Base?
Cloud base is the height where rising air cools enough for water vapor to condense into cloud droplets. In everyday weather terms, it is the bottom of the cloud layer you see.
A common way to estimate cloud base uses the temperature–dew point spread. When temperature and dew point are close, the air is near saturation and the cloud base tends to be lower. When they are far apart, the cloud base tends to be higher.
This cloud base calculator is often used as a quick estimate in aviation. It uses temperature (°F), dew point (°F), and elevation (ft) to output a cloud base altitude (ft) and the approximate cloud temperature (°F) at that base.
Cloud Base Formula
A widely used rule-of-thumb estimates cloud base above ground level (AGL) from the temperature–dew point spread. Then you can convert to an approximate altitude above mean sea level (MSL) by adding elevation.
T and Td are in °F. 222 ft/°F is a common approximation (close to 1000 ft per 5°F spread).
Use your local elevation (field elevation) in feet.
Uses an approximate dry adiabatic cooling rate of about 5.4°F per 1000 ft.
A bigger spread usually means a higher cloud base.
This estimates the air temperature at the altitude where the cloud base forms.
Cloud Base Altitude Quick Chart
Approximate cloud base above ground level (AGL) using CloudBase(AGL) ≈ (T − Td) × 222.
| Temp–Dew point spread (°F) | Cloud base (AGL, ft) |
|---|---|
| 2 | 444 |
| 4 | 888 |
| 6 | 1332 |
| 8 | 1776 |
| 10 | 2220 |
| 12 | 2664 |
| 15 | 3330 |
| 20 | 4440 |
How to Calculate Cloud Base
- 1
Enter air temperature (°F).
- 2
Enter dew point (°F).
- 3
Enter elevation (ft).
- 4
The calculator finds the temperature–dew point spread, estimates cloud base (AGL), adds elevation to get cloud base altitude (ft), and estimates cloud temperature (°F).
Frequently Asked Questions
A common estimate is CloudBase(AGL, ft) ≈ (T − Td) × 222, where T and Td are in °F. Add elevation to estimate altitude above sea level.
Many aviation quick-calculations use the dew point spread rule-of-thumb: (T − Td) × 222 for cloud base AGL in feet (when using °F).
Dew point reflects how much moisture is in the air. The closer dew point is to temperature, the sooner rising air becomes saturated, which lowers the cloud base.
No. It is a fast approximation. Real cloud bases can differ due to pressure changes, mixing, and layers of moisture that the simple spread method does not capture.
This calculator estimates cloud base and the temperature at that base. Freezing level requires finding the altitude where temperature reaches 32°F, which depends on a separate lapse-rate or atmospheric profile.