For many years, Family Matters has provided updated estimates of the cost of raising children. Issue no.53 carried two papers which calculated new sets of estimates based on two different methodological approaches: Costs of children in Australian households: new estimates from the ABS Household Expenditure Survey by Ma. Rebecca Valenzuela from the Melbourne Institute of Applied Economic and Social Research; and Budget standards and the costs of children by Peter Saunders from the Social Policy Research Centre, University of New South Wales. These are now followed up with this article by researchers from the National Centre for Social and Economic Modelling (NATSEM) at the University of Canberra, who develop a third approach, often termed the ISO-PROP method. The estimates described here come out mid-way between the other two. The calculations take account of family income and family size, and are expressed in terms of percentage differences - which should allow readers to update cost estimates as new family expenditure data are released in future waves. The methodology is described, and estimates of average costs are provided.