Free · Physics models
Cumuliform Cloud-Base Approximation
Estimate cloud-base altitude and parcel temperature from surface temperature, dew point and surface elevation.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
At 20°C and a 10°C dew point, the estimated base is about 1,247 m above the surface; at 100 m surface elevation it is about 1,347 m above sea level.
AGL height = (T°F − Td°F) × 1000 ft/4.4; base altitude = elevation + AGL; parcel cooling ≈ 5.4°F per 1000 ft.
Worked example
Enter these known values and leave the other values blank.
- Temperature
- 20 °C
- Dew point
- 10 °C
- Elevation
- 100 m
- Cloud base altitude
- 1347 m
- Cloud temperature
- 7.727 °C
Assumptions and limitations
- This is an approximate lifted-parcel estimate for cumuliform clouds using surface temperature and dew point. It is not an observed cloud ceiling or an aviation weather report.
- The captured model uses Fahrenheit internally with a 4.4°F convergence per 1,000 ft and 5.4°F dry-parcel cooling per 1,000 ft.
- Surface elevation and output altitude share the same vertical datum; subtract elevation to obtain height above ground. Dew point cannot exceed temperature.
- Enter known quantities and leave the unknown blank. Editable quantities support inverse solutions and locks; inconsistent locked quantities are reported. Unit selectors convert the quantity independently of its display.
Common questions
Is the result above ground or sea level?
The altitude includes entered surface elevation. Subtract that elevation to obtain height above ground.
Can I use this as a reported aviation ceiling?
No. It estimates a lifted surface parcel and cannot replace measured or forecast aviation cloud information.
How do I use the inverse calculation?
Clear the quantity you want to find and enter the remaining known values in their selected units. The model can only solve branches with enough independent information.
References
The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.