‘A demographer’s toolbox’ looks at the tools, models, methods, assumptions, and uncertainties within the practice of demography. Demographers need to know that they are really finding out the things they want to know and that their methods and sources of data are robust and are accurately answering their questions. There are four main sources of demographic data: census, registration records, surveys, and ethnographic material. The 1980s and 1990s saw an increasingly sophisticated adoption of mathematical models, needed to cope with the growing availability of demographic data. The arrival of modern computing methods also transformed the power of demographic analysis. Recently, probability, competing risks, hazard functions, and bio-markers have been added to the demographer’s toolbox.