The Marriage Calculator helps policy makers, researchers, and the general public to understand the financial consequences of marriage for individuals earning less than about $40,000 per year. Users can see how taxes and public assistance change when a couple’s living arrangement changes from living apart to cohabiting to married. This is a general use tool. Social service agencies in the community are the best source of exact information. This tool uses the 2003 tax laws and benefits rules, and it does not take some possible situations into consideration in calculating results (for example, information about whether a family lives with other relatives or whether a family member is disabled is not included in the calculations). (Author abstract, modified)