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Lapse Rate Calculator

Work out lapse rate instantly with clear inputs, formula shown and shareable results.

About Lapse Rate Calculator

Lapse rate is the temperature fall per kilometre of altitude. Fourteen degrees over 2000 m is 7 C/km - between the saturated adiabatic rate of about 6 and the dry adiabatic 9.8, so the atmosphere is conditionally unstable: stable for unsaturated air but unstable once cloud forms. Negative rates are inversions, which trap pollution.

Formulas

Environmental lapse rate

rate = (lower temp - upper temp) / height difference x 1000

Reference rates

dry adiabatic 9.8 C/km, saturated about 6 C/km, standard atmosphere 6.5 C/km

Worked example

With the default values below, Lapse Rate Calculator returns Environmental Lapse Rate of 7.000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Temperature at the lower level
18 C
Temperature at the upper level
4 C
Height differenceminimum 0 m
2,000 m

Results

Environmental Lapse Rate
7.000 C/km
Atmospheric Stability
Conditionally unstable
Difference From The Dry Adiabatic Rate
-2.800 C/km
Temperature 1000 m Higher
11.0 C

Step by step

  1. 1Values used
  2. 2Environmental lapse rate
  3. 3Reference rates
  4. 4Environmental Lapse Rate= 7.000 C/km
  5. 5Atmospheric Stability= Conditionally unstable
  6. 6Difference From The Dry Adiabatic Rate= -2.800 C/km
  7. 7Temperature 1000 m Higher= 11.0 C

Assumptions and limits

  • The result is derived only from the 3 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 3 decimal places, 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

What does conditional instability mean?

Unsaturated air resists rising but saturated air accelerates upward, so cloud once formed can develop into deep convection.

Why do inversions cause smog?

Because warm air above cold traps the surface layer, so pollutants cannot disperse upward and concentrations build.

Related Calculators

Lapse Rate Calculator – Calculate Environmental Lapse Rate