mWcm2

mW/cm2 is a unit of radiant flux density used to express irradiance, meaning how much light power passes through or falls on a given area. It corresponds to milliwatts per square centimeter and is commonly written as mW/cm^2 or mW cm−2. In SI terms, 1 mW/cm^2 equals 10 W/m^2, since one square centimeter is 1e-4 square meters. Conversely, 1 W/cm^2 equals 10,000 W/m^2. The unit is widely used because it provides convenient values for moderate light intensities over small areas.

Usage and applications

The unit appears in fields such as optics, photochemistry, photobiology, laser processing, UV curing, and solar energy research. It is often employed to report irradiance from light sources, solar simulators, or UV lamps. Measurements are typically made with calibrated radiometers or photodetectors that have known spectral responsivity. Depending on the application, results may be given for a specific wavelength range or as total radiant flux density across the spectrum.

Typical ranges and interpretation

For sunlight at Earth’s surface, irradiance is on the order of tens to hundreds of mW/cm^2 (roughly 100–150 mW/cm^2 under bright conditions). In photochemical or photopolymerization processes, mW/cm^2 values help quantify exposure time and dose, balancing processing speed with material sensitivity and safety considerations. Because mW/cm^2 is not an SI base unit, researchers often convert to W/m^2 for SI consistency.

See also

W/m^2, irradiance, radiometry, photodetector, spectral irradiance.