Lifted Condensation Level Calculator
The lifted condensation level (LCL) is the altitude above the surface at which an air parcel, lifted dry adiabatically, first reaches saturation. At the LCL, water vapor condenses and cumulus clouds begin to form. The LCL is a critical parameter in convective meteorology: a low LCL favors tornado development, while a high LCL indicates a drier environment. This calculator uses the standard approximation (125 m per degree Celsius of dewpoint depression) derived from the difference in dry adiabatic and dewpoint lapse rates, which is accurate to within 100-200 m for typical surface conditions.
LCL formula
LCL (m) = 125 * (T - Td)
Where T is surface temperature in Celsius and Td is surface dewpoint in Celsius. The factor 125 m/C comes from dividing 1000 m by the dry adiabatic lapse rate minus dewpoint lapse rate in Celsius per 1000 m (8 C/km - 0 C/km = 8 C/km, giving 1000/8 = 125). LCL in feet = LCL in meters / 0.3048.
LCL and severe weather assessment
- LCL below 1000 m (3,300 ft): favorable for tornadoes and low cloud bases in convective environments.
- LCL 1000-2000 m (3,300-6,600 ft): moderate; thunderstorm bases typical of humid regions.
- LCL above 2000 m (6,600 ft): high bases; downdraft evaporation increases; dry microbursts more likely.
- Storm Prediction Center (SPC) operational forecasters consider LCL below 800 m a significant tornado ingredient.
LCL calculator: frequently asked questions
What is the lifted condensation level (LCL)?
The LCL is the altitude at which a parcel of air, lifted dry-adiabatically from the surface, becomes saturated and cloud formation begins. It is a key parameter in convective weather forecasting. The LCL approximates the base of convective clouds such as cumulus and cumulonimbus.
How does the Bolton (1980) formula calculate LCL?
Bolton (1980) gives the LCL temperature as: T_LCL = 1 / (1/(Td - 56) + ln(T/Td)/800) + 56, where T and Td are in Kelvin. The LCL pressure is then P_LCL = P * (T_LCL/T)^(Cp/Rd), and the height is derived from the hypsometric equation. A simpler common approximation is LCL height (m) = 125 * (T - Td) in Celsius.
What is the difference between LCL, LFC, and EL?
The LCL is where a parcel first reaches saturation. The Level of Free Convection (LFC) is where the parcel becomes positively buoyant and rises freely. The Equilibrium Level (EL) is where the parcel loses buoyancy at the top of a thunderstorm. LCL is below LFC in unstable air, and the difference between them indicates convective inhibition (CIN).
Why does a lower LCL indicate more severe weather potential?
A lower LCL means cloud bases are closer to the ground. In supercell thunderstorm environments, low LCLs (below 1000 m) are associated with higher tornado potential because the condensation funnel can reach the ground more easily. High LCLs (above 2000 m) reduce this risk but increase downdraft evaporation, which can produce dry microbursts.
Can the LCL be calculated from relative humidity?
Yes. Using the approximation LCL (m) = 125 * (T - Td), and noting that Td can be derived from T and RH using the Magnus formula, you can compute LCL from temperature and relative humidity alone. This simplified approach is accurate to within 100 m for typical conditions.
Official sources
- NOAA Storm Prediction Center: SPC Sounding Analysis.
- Bolton, D. (1980): The computation of equivalent potential temperature. Monthly Weather Review, 108, 1046-1053. Via AMS Journals.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.