-This work deals with the calculation of the uncertainty of the exogenous respiration rate (R ex ) and the total oxygen consumed (OC T ) derived from a single open respirometric profile. Uncertainties were evaluated by applying a linear error propagation method. Results show that standard deviations (SD) of R ex and OC T depend not only on the SD of the dissolved oxygen (σ C ) and k L a (σ kLa ), but also on the SD of the derivative term (dC/dt) of the oxygen mass balance equation (σ b ). A Monte Carlo technique was employed to assess σ b ; a power law expression for the dependence of σ b as a function of σ C , the time window (t w ) and the sampling rate (Δt) was proposed. The equations obtained in the present work are useful to calculate suitable conditions (e.g., biomass concentration, k L a) that minimize the coefficient of variation corresponding to R ex and OC T .