A new proportional weighting algorithm is proposed to bridge multiple-race counts to single-race estimates based on 2010 Decennial Census data. The proposed weighting method is based on Census data alone with traceable procedure and reproducible results. It enables researchers to estimate population size of any race category of interest at any level of granularity stratified by other demographic information available in the Census data. If researchers have specific criteria or priorities for classifying certain races, the proposed algorithm can be easily modified to meet their specific needs. The new algorithm provides an intuitive and straightforward alternative for determining single-race population estimates. As an illustration of this approach, we provide the population estimates of the five most populous ethnic groups in Hawaii using the 2010 Census data.