Many social survey datasets available through the UK Data Service include weighting variables, or weights. Data producers calculate weights to make the data better represent the population it is designed to represent. A weighting variable assigns a value to each case in the dataset to indicate how much they should be represented in the analysis. Weights can be applied in statistical packages such as SPSS and Stata and can be vital for ensuring that results relate to the population of interest. This guide explains the main reasons for using weights, how weights work and how to use weighting variables in statistical analyses.