Are Styrofoam Cups Microwave Safe? Is Really Safe

Styrofoam cups are generally not safe to use in the microwave because they are made from polystyrene, which is a type of plastic that is not safe for microwaving. When polystyrene is heated in the microwave, it can release harmful chemicals into your food or drink. This can be especially dangerous if you are using the cup to heat up food or beverages that are intended for consumption.

Nonetheless, you can still microwave styrofoam cups. However they’re not meant to be microwaved more than once. 

Hence, you can find microwave-safe plastics and polystyrene containers, and cups that are regulated by the Food and Drug Administration (FDA).

That means microwave-safe labels are placed on these polystyrene products that have been tested to ensure their safety.

In this article, we’re going to look at why styrofoam cups are microwave safe and what you need to know about microwaving styrofoam cups. 

What Is Styrofoam?

Styrofoam is a word trademarked and used by The Dow Chemical Company to refer to the polystyrene foam used by the building industry. 

What Is Styrofoam

Most countries, including Canada and the US, use the term incorrectly to describe a type of expanded polystyrene foam used in making disposable take-out containers, plates, and coffee cups.

These after products of polystyrene became popular due to their insulating properties and how cheap the products are in the market.

Due to the health and environmental concerns of polystyrene, many countries have banned this product as it acts as a potential risk to humans and animals. 

Are Dart Styrofoam Cups Microwavable?

Dart foam polystyrene may vary in performance depending on the type of food being heated, the length of the heating time, and the intensity of the microwave oven.

However, due to the possibility of getting different results when using a microwave to heat different beverage substances, we recommend not using a Dart foam polystyrene in a microwave. 

The temperature at which different beverages would heat up in a dart styrofoam differs and this can lead to polystyrene particles leaking into the beverage. This is why we do not recommend using dart styrofoam cups. 

Why Are Styrofoam Cups Microwave Safe?

Styrofoam cups are made from polystyrene particles which is a chemical compound that isn’t safe to microwave. 

Styrofoam cup

However, these cups are heat-resistant and sturdy, which makes it fine to microwave them. 

You don’t have to use these cups in a microwave forever. You have to take note of when the cup shows signs of damage or begins to pit to stop use.

So why are styrofoam cups microwave safe?


Styrofoam is made from petroleum based products which include chemicals like benzene and styrene. It is composed of 98% air which makes it durable and lightweight. 


Based on styrofoam’s air composition, it is seen as a good material for insulation. As a result of its insulation properties, Styrofoam cups provide longer-lasting hot and cold temperatures. 


Styrofoam cups are best used to serve hot chocolate and coffee. Due to its properties, most people have extended to using styrofoam to serve chili, stews, and soup. 


Styrofoam is affordable, strong, and preserves heat over a long period. They can be found almost anywhere. 

Note that all styrofoam cups are not alike and react the same in a microwave. So you have to check for a microwave safe tag beneath the cup. 

If there is no tag, you can take it that the cup is not microwave safe and not recommended for use in a microwave or else the chemicals would leak into the contents it holds.

What To Know About Microwaving Styrofoam Cups

Many People Take Advantage Of The Insulating Properties And Durability Of Styrofoam, But That’s Not How It Should Be Done. There Are Certain Things One Needs To Know About Microwaving Styrofoam Cups Before Doing It.

Styrofoam Cup Microwave

Here are a few important things one needs to know before microwaving styrofoam cups. 

Crosscheck Styrofoam Cups

Before microwaving any styrofoam cup, check to see if there are any cracks or scratches on the surface of the cup. Cracked, damaged, old, or degraded styrofoam cups can leak harmful chemical substances into your beverage. 

No Dual Reheating

Styrofoam cups are meant to be used once in a microwave. Do not reheat a styrofoam cup after the initial reheating action. 

Heat Regulation 

Turn down the power level of your microwave to medium to use the styrofoam cup to reheat beverages and food. 

Increase the temperature level of the microwave in 30 seconds increment if the temperature level is not enough to heat up the content of the cup. 

Reheating causes uneven heat pockets to form in food items while they’re in the microwave. Therefore, you need to stir your food contents while reheating to avoid overheating. 


When taking out the heated styrofoam cup from the microwave, not that the outside surface of the cup might be cool to touch but the content of the cup can be very hot. Therefore, handle the cup with caution while taking it out of the microwave.

Food Transfer

After reheating food or beverage in a styrofoam cup, transfer the content of the cup to the proper containers like ceramic mugs and bowls, glass plates and cups, and pyrex mugs before consumption.


If you want to microwave food or beverage using a styrofoam cup, avoid the polystyrene coffee cup as they are not microwave-safe certified which makes them hazardous for reheating drinks and food.

Check for a microwave-safe tag before using any cup as it certifies the cup is clear of any potential health risk. If you have any concerns about overheating styrofoam cups, then find microwave-safe cups to use.