APA Format for Numbers With Decimal Points

American Psychological Association or APA style includes guidelines for writing in social sciences fields such as history and education. Papers in the social sciences often include data presented in tables and figures. The sixth edition of the Publication Manual of the American Psychological Association details the recommended format for numbers that include decimal points.

Numbers written in APA style should usually contain two decimal places, according to the University of West Florida. In some cases, however, the precision of a measurement requires additional decimal places. For example, if p = .001, you must include three decimal places. The Purdue Online Writing Lab recommends using decimals consistently; don't change the number of decimal places within a table.

Leading zeros refer to the zero placed before a decimal point. According to the American Psychological Association, you should only include a leading zero when the value has the potential to exceed 1.0. For example, if you are discussing the median time people spend reading every day, such as 0.36 hours, you should use a leading zero because people can read for more than an hour. If your number can never exceed 1.0, for instance if you are discussing a p value, such as .01, you should not include a leading zero.