School Resources

How to Keep Food Warm in a Lunch Box



Last Updated: Nov 2, 2021

You’ve spent hours in the kitchen making your famous lasagna. You lovingly pack your lasagna in your child’s lunch box only for them to come back after school to tell you it was ice cold. While cold lasagna might not be the end of the world, it’s safe to say warm lasagna with gooey cheese is just a bit more delightful to the palate. If you’re searching for ways to keep food warm when you’re out and about, look no further. We’ve gathered some of the best tips and tricks on how to keep your food warm in a lunch box.

Ways to keep food warm in a lunch box

Here are our top ideas for how to easily store food for lunch so that it doesn’t get cold:

1. Insulated containers

Insulated lunch boxes with nutrition food.

The best way to keep food warm in lunch boxes is to invest in some insulated food containers. These containers function similarly to a thermos. Thermoses and insulated food containers can keep the food content warm for a period of time without electricity or reheating. This is typically accomplished by the container forming a tight vacuum seal where hot air won’t escape or by having insulated lining or materials in the container.

When searching for insulated containers, look specifically for containers with the word “insulated” in the description or look for food containers that are made of stainless steel. While there are products that will include premium insulated technology, food containers made from stainless steel will function likewise. When hot food is placed in a stainless steel container, the stainless steel will also heat up, keeping the contents warm for a few hours.

2. Boiled water

Another way to keep your food warm for a longer period of time is to use boiling water to heat your stainless steel food container. In the morning, before you pack your lunch, boil water and pour the hot water into your stainless steel container. Close the lid and let the water sit until you heat up the food that will go into the container.

Once you are ready to pack your lunch, warm up your food. Empty the hot water from your container and dry the inside. Place the warmed food into your insulated container and seal the lid. The stainless steel should be hot from the boiled water and will your food warmer for a longer period of time.

3. Foil

A cost-efficient way to keep your food warm in a lunch box is by wrapping hot food items in aluminum foil. Although wrapping hot items in foil will not keep it warm for hours on end, it will keep the food warm for a short period of time.

Foil is technically not insulated; however, when hot food is placed inside, the foil will temporarily warm in temperature, simultaneously keeping the food warm. You can also try wrapping the foil with plastic saran wrap or a towel to prolong the warm temperature.

5. Hot water bottle

Keep your food warm in a lunch box by placing a hot water bottle inside. Hot water bottles are commonly made from rubber or thermoplastic material where the inside is hollow so you can fill it with warm water. Most often, hot water bottles are used by individuals feeling under the weather and use the hot water bottle to soothe aching parts of the body.

Before filling your hot water bottle, check for any rips or holes. Once the bottle has been thoroughly inspected, you can fill it with water. Do not use boiling water. Boiling water can weaken the material and cause it to rip or become damaged. Use boiled water that has been slightly cooled to fill your bottle, and make sure not to overfill it.

It is recommended to fill the bottle three-quarters of the way and seal the lid. To keep food warm, place the hot water bottle at the bottom of your lunch box and carefully set the food container you want to keep warm on top of the hot water bottle.

6. Insulated thermal bags

Similar to the idea of placing hot food in foil and a towel, insulated thermal bags essentially do the same thing—but better. These thermal bags reflect heat into the contents inside and are easily transportable. Insulated thermal bags commonly come in packs and are often at the cheaper end of the price spectrum. After using a bag, you can rinse and reuse it multiple times, or if it becomes too worn, you can discard it and use a clean, new one.

7. Insulated lunch box

Bag cooler bright green for carrying and storing products

For an extra layer of warmth, store your insulated food containers in an insulated lunch box. Nowadays, there are many options to find an insulated lunch box that fits your style and price point. Insulated lunch boxes can come with various features, including insulated lining, multiple compartments, special sections for heating packs or hot water bottles, waterproof interiors, and more. Research the best type of insulated lunch box that will fit your lifestyle and budget.

8. Separate hot and cold items

Although you’re dealing with a limited amount of space, do your best to separate hot and cold items. While you may have individual containers for hot and cold food items, you can further keep them separated by using a physical divider. Try using neutral items like napkins or utensils to add a small division between your hot and cold containers. Doing this will ensure the temperatures of both your containers stay as controlled as possible.

Now that you know how to keep food warm in a lunch box, it’s time to pack!

We hope these tips will help keep your food warm as you pack your lunch box for the week. If you find that your schedule is too busy and you need a helping hand, you can easily shop online for grocery items and more via Instacart! Choose your items online, and an Instacart shopper will pick out and bag the items for you. For additional convenience, you can pick them up curbside or have your items conveniently delivered straight to your home.



Instacart is the leading grocery technology company in North America, partnering with more than 1,400 national, regional, and local retail banners to deliver from more than 80,000 stores across more than 14,000 cities in North America. To read more Instacart posts, you can browse the company blog or search by keyword using the search bar at the top of the page.

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