The present study demonstrates the possibility of estimating species numbers of animal or plant communities from samples using relative abundance distributions. We use log-abundance–species-rank order plots and derive two new estimators that are based on log-series and lognormal distributions. At small to moderate sample sizes these estimators appear to be more precise than previous parametric and nonparametric estimators. We test our estimators using samples from 171 published medium-sized to large animal and plant communities taken from the literature. By this we show that our new estimators define also limits of precision.