Here’s how to tell if your fridge is at the best temperature for keeping your food safe and fresh.

Refrigerators are a true modern miracle—they allow us to preserve food in a way that has completely changed our relationship to how we eat. They’re now so ingrained in our daily lives that it’s easy to take them for granted. If you’re like me, you may realize you know very little about your fridge, including what temperature it’s actually supposed to be.

The USDA recommends storing food at or below 40°F. Above that threshold, food will begin to spoil much faster. But you really want your fridge to be closer to 35°F, so that it has a little bumper to keep food cold when you’re opening and closing the doors.

Some newer refrigerators have the ability to control that specific temperature, but the majority of fridges still just have 5 settings, with 1 being the coldest and 5 the warmest. Even if you have a temperature gauge built into your fridge, it’s worth checking its accuracy by putting a thermometer in your fridge and closing the door for about 20 minutes. If the thermometer reads above 35°F, turn the temperature down. If it’s lower, you can turn the temperature up. Check the fridge a couple of times a year, and know that you may need to adjust the temperature settings in the summer or winter when the temperature of your house affects how hard the cooling unit inside the fridge has to work to cool it down.

If the contents at the back of your fridge starts to freeze, this may be an indication that you’re not getting enough airflow. The coldest air can get stuck at the back, causing that food to freeze while other foods further away from the vents aren’t getting their fair share. The most likely culprit for this is that your refrigerator is too full. Try reorganizing to give the air a little more space to move around, and turn the temperature dial up one click.