There are some things in life we can successfully manage by guesswork. How much cinnamon goes in the apple pie? A little extra never hurt anybody. How much cheese belongs in a casserole? We all know the answer is "more." And how long should we visit with a friend who says, "I have just one quick thing to tell you"? Well, that depends on how much coffee is left in the pot!

But when it comes to the temperature of your refrigerator and freezer, guessing is not the best plan. These hardworking appliances keep our food safe, protect our grocery dollars, and help us avoid the kind of kitchen adventure nobody wants to remember.

Fortunately, getting the temperature right is easy, and a few simple habits can make a big difference.

According to the U.S. Department of Agriculture, your refrigerator should be kept at 40 F or below, and your freezer should be set at 0 F.

That refrigerator temperature is important because bacteria that can cause foodborne illness multiply more rapidly when perishable foods get too warm. Keeping the refrigerator at 40 F or colder helps slow their growth. Your freezer, at 0 F, keeps food frozen and maintains its quality, although freezing does not destroy all harmful bacteria.

Here is a little rule worth remembering: 40 F for the refrigerator, 0 F for the freezer.

Simple enough to put on a sticky note, tape inside a cabinet, or repeat to anyone in the family who insists the refrigerator is cold because they can see their breath when the door is open. (That last part may be an exaggeration, but you get the idea!)

How to change the temperature? Many refrigerators have a numbered dial or digital temperature setting. The trouble is that a setting of "3" or "medium" doesn't necessarily tell you the actual temperature inside. Appliance designs, room temperatures, how full the refrigerator is, and how often the door opens can all affect performance.

The best solution? Use an appliance thermometer, available just about anywhere including your favorite supermarket.

Place a refrigerator thermometer in the center of the refrigerator compartment, away from the walls and cooling vents. Put another thermometer in the freezer. Check the readings after the appliances have had time to stabilize, and adjust the settings as needed.

If your refrigerator is above 40 F, make the necessary adjustment and recheck the temperature. If it cannot maintain a safe temperature, it may need attention from a qualified appliance technician.

A thermometer is a small investment that can prevent a much bigger loss. After all, throwing away groceries is painful enough without having to throw away the money you planned to spend on something fun!

Next, your refrigerator works best when cold air can circulate around the food. Packing every shelf as tightly as a suitcase before vacation can interfere with that circulation.

Keep food organized, leave room around air vents, and avoid placing hot leftovers directly into an overcrowded refrigerator. Divide large amounts of food into shallow containers so they cool more quickly. Perishable food should generally be refrigerated within two hours, or within one hour when the temperature is above 90 F.

At the same time, don't leave your refrigerator nearly empty for long periods if you can help it. The goal is not to win a refrigerator-stuffing contest or create a museum exhibit featuring three jars of mustard. The goal is sensible storage and good airflow.

Also, keep the refrigerator and freezer doors closed as much as possible. Standing in front of the open refrigerator contemplating your life choices may be a time-honored tradition, but it isn't helping the temperature!

Then, there's the freezer. A freezer set at 0 F keeps food frozen solid and helps preserve quality over time. Label packages with the food name and date, rotate older items forward, and package foods securely to help prevent freezer burn.

Freezer burn can dry out food and affect its taste and texture. It isn't, by itself, a food-safety concern, but it can turn that beautiful roast into something resembling a science experiment.

If the power goes out, keep refrigerator and freezer doors closed. An unopened refrigerator generally keeps food cold for about four hours. A full freezer can maintain its temperature for approximately 48 hours, or 24 hours if half full, provided the door stays closed. Check food temperatures before deciding what is safe to keep.

Now, let's talk maintenance. Make checking your appliance thermometers part of your regular kitchen routine. Clean spills promptly, inspect door seals for damage, and follow the manufacturer's instructions for cleaning coils and maintaining the appliances.

Remember, too, that food safety isn't determined by smell or appearance alone. Food can contain harmful bacteria without looking or smelling spoiled. When in doubt, follow USDA food-safety guidance rather than relying on a sniff test performed by the family expert.

The payoff is confidence. Keeping your refrigerator at 40 F or below and your freezer at 0 F is one of those small household habits that pays off every day. It helps protect your family, reduce unnecessary food waste, and make the most of the groceries you bring home.

So grab a thermometer, check those temperatures, and give yourself a little pat on the back. You have taken a simple step toward a safer, better-organized kitchen.

And the next time you open the refrigerator and stand there wondering what to make for supper, at least you'll know one thing for certain: Whatever you decide, it's being kept at the right temperature. Now, if only the refrigerator could suggest a menu, wash the dishes, and tell us what happened to the leftovers we were saving for tomorrow!

One can dream. In the meantime, stay cool, keep smiling, and remember that a little kitchen know-how goes a long way.

Mary invites you to visit her at EverydayCheapskate.com, where this column is archived complete with links and resources for all recommended products and services. Mary invites questions and comments at https://www.everydaycheapskate.com/contact/, "Ask Mary." This column will answer questions of general interest, but letters cannot be answered individually. Mary Hunt is the founder of EverydayCheapskate.com, a frugal living blog, and the author of the book "Debt-Proof Living."

Photo credit: Ello at Unsplash