Brewer spectroradiometers are widely used instruments that have been monitoring global solar ultraviolet (UV) irradiance since the 1990s, playing a key role in solar UV research. The uncertainties of these measurements are rarely evaluated even though they are essential to determine the quality of these measurements. In this work, the uncertainty of 10 Brewers is estimated using the Monte Carlo method, showing that Brewers’ relative uncertainty is less than 5 % for wavelengths above 310 nm.