When you got home after a weekend excursion with your family, a business trip, or vacation, did you ever notice that your digital clocks were flashing at the incorrect time?

You quickly find out that there was a power outage during your absence, but you can’t really tell when or for how long. As a result, it is also impossible for you to tell how long the food in your freezer may have thawed, gone bad, and then been frozen again.

Following Hurricane Matthew’s 2016 devastation of portions of the United States, Sheila Pulanco Russell posted a thoughtful advice on her Facebook wall for anyone forced to leave their homes.

But this tip is helpful for anyone who will be away from home for an extended period of time and will ease your mind about whether the food in your freezer is still edible or needs to be thrown out right away.

Three commonplace objects are used in this easy-to-do trick: a coin, a mug, and some tap water.

Sheila provided a useful advice for people fleeing the coast in a Facebook post that received hundreds of thousands of reactions and likes in a matter of minutes. She writes:

I’ve heard a fantastic advice for those of you who are fleeing the coast. We refer to it as the one-cup tip. You fill your freezer with a cup of water. Place a quarter on top of it and return it to your freezer after it has solidified. In this manner, you may determine whether your food went bad and just refroze or whether it stayed frozen while you were away when you return after being evacuated.

You should discard the food if the quarter has defrosted and dropped to the bottom of the cup. However, your food can still be fine if the quarter is either at the top or in the center of the cup. It would also be a fantastic idea to keep this in your freezer at all times so you have this handy tip in case of an unexpected power outage.