Estimating fish fecundity is important for developing accurate population models and informed management decisions. Fecundity can be determined by tedious, complete oocyte counts. Researchers save time by counting a subsample of oocytes, measuring the subsample and total ova volume and weight, and extrapolating to produce fecundity estimates using volumetric and gravimetric methods. Volumetrically- and gravimetrically-generated fecundity estimates from 70 brook trout (Salvelinus fontinalis, range 143–356 mm) captured from Long Creek, Oregon, were compared to total oocyte counts to evaluate the accuracy and precision of each method. The average total oocyte count was 775 (SD ± 354.8). The mean difference between total oocyte count and extrapolated count based on the gravimetric method was 111.2 (SD ± 154.0) and 165.9 (SD ± 279.0) for the volumetric method. Gravimetric and volumetric fecundity estimates were closely correlated with total oocyte counts, although both were positively biased. Volumetric estimates were on average 1.100 times true fecundity (95% CI = 1.05, 1.15) and gravimetric estimates were 1.086 times true fecundity (95% CI = 1.05, 1.12).