Uncertainty related to estimates of krill green weight from catches has recently been an issue raised repeatedly within CCAMLR for a number of years, resulting in a modification to the C1 form implemented for the fleet in 2012. There are at present three Norwegian vessels operating in the krill fishery for Euphausia superba in the Antarctic. These vessels have in recent years contributed to 50-60 % of the total krill harvest, and reliable uncertainty estimates from these vessels will therefore be important contributions to an estimate of total uncertainty in catch weight. Here, we present the procedures for uncertainty estimation on board the Norwegian vessels, including how measurements are carried out in practice and transferred to the C1 forms. We also present a brief evaluation of results and procedures.