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Cloud Base Height Calculator

Work out cloud base height instantly with clear inputs, formula shown and shareable results.

About Cloud Base Height Calculator

Rising air cools at 9.8 C per kilometre while its dew point falls only 1.8 C per kilometre, so the two converge at 8 C per kilometre - which gives a cloud base of 125 m per degree of surface spread. A 10 degree spread puts the cumulus base near 1250 m, or 4100 feet, with a temperature there around 11.8 C.

Formulas

Cloud base

height(m) = (temperature - dew point) x 125

Convergence rate

dry adiabatic 9.8 C/km minus dew point lapse 1.8 C/km = 8 C/km

Worked example

With the default values below, Cloud Base Height Calculator returns Cloud Base Height of 1,250. Change any input above and every figure here is recalculated in your browser.

Inputs used

Surface air temperature
24 C
Surface dew point
14 C

Results

Cloud Base Height
1,250 m
Same Height In Feet
4,101
Temperature-Dew Point Spread
10.0 C
Temperature At Cloud Base
11.8 C

Step by step

  1. 1Values used
  2. 2Cloud base
  3. 3Convergence rate
  4. 4Cloud Base Height= 1,250 m
  5. 5Same Height In Feet= 4,101
  6. 6Temperature-Dew Point Spread= 10.0 C
  7. 7Temperature At Cloud Base= 11.8 C

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Does this work for all cloud types?

Only for convective cumulus formed by surface heating. Layered stratus and frontal cloud form by other mechanisms at other heights.

Why do pilots use 400 feet per degree Fahrenheit?

It is the same rule in imperial units - 125 m per degree Celsius works out at about 227 feet per degree Fahrenheit, often rounded in practice.

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