A distortion-weighted glimpsing metric developed for estimating monaural speech intelligibility is extended to predict binaural speech intelligibility in noise. Two aspects of binaural listening, the better ear effect and the binaural advantage, are taken into account in the new metric, which predicts intelligibility using monaural target and masker signals and their location, and is therefore able to provide intelligibility estimates in situations where binaural signals are not readily available. Perceptual listening experiments were conducted to evaluate the predictive power of the proposed metric for speech in the presence of single and multiple maskers in anechoic conditions, for a range of source/masker azimuth combinations. The binaural metric is highly correlated (ρ > 0.9) with listeners' performance in all conditions tested, but overestimates intelligibility somewhat in conditions where multiple maskers are present and the target speech source location is unknown.