Salt reduction is one of the most important lifestyle modifications for the prevention of hypertension. The health promotion law regulates the labeling of the nutrient content of food in Japan and, the level of sodium, not salt (sodium chloride), has to be printed on the labels of manufactured foods. In order to control their salt intake, consumers need to apply a conversion factor to the sodium levels listed on the labels to obtain the salt equivalent. However, it is not known whether people have the knowledge appropriate for making the conversion. We carried out a questionnaire survey at the 7th National Shokuiku (food education) Conference in 2012, asking subjects to determine the salt equivalent of 1000 mg of sodium on food labels. We also asked about the target values of salt reduction in grams in the Dietary Reference Intakes for Japanese 2010 (DRI2010) and the Guidelines for Management of Hypertension 2009 by the Japanese Society of Hypertension (JSH2009). We analyzed the data from 683 respondents (169 men and 514 women); only 13.3% of respondents gave a correct answer for the salt equivalent of 1000 mg of sodium (2.50-2.60 g), whereas 61.8 and 40.4% of respondents chose the correct target values for salt reduction according to DRI2010 and JSH2009, respectively. In conclusion, few people could convert sodium content to salt, which suggested difficulty in using food labels to control their salt intake. Salt content in grams, not sodium content, should be labeled on food packages for effective salt reduction and prevention of hypertension.