The ideal temperature for a refrigerator is 40 degrees Fahrenheit or below, according to the Food and Drug Administration (FDA) . This temperature inhibits the growth of microorganisms that can cause foodborne illnesses, such as salmonella, listeria, and E. coli. However, its important to note that the temperature controls on many fridges only allow you to choose from a series of numbers, usually 1 through 5, with 1 being the coldest and 5 being the warmest. Therefore, its recommended to use a refrigerator thermometer to ensure that the temperature is set correctly. Most experts recommend that the ideal temperature setting for a refrigerator is between 35-38°F (1.6-3.3°C) . Its also important to keep perishable items cold, but not so cold that vegetables lose their freshness. If your refrigerator is older, it may not maintain the same temperature all over, so its recommended to put two thermometers in an older fridge and check both regularly.