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Is your child’s lunch routine in a rut? Learn how to keep food warm in lunch box to switch things up!

An overhead image of soup in a thermos with crackers.

There’s something so comforting and filling about a warm lunch. It’s like a bite of home, even in the middle of a busy classroom or crowded school cafeteria. If your child is ready for a change or you’re looking to incorporate some variety into their lunch menu, there are a few tricks to sending warm food in their lunch box safely.

In this post, we’ll break down the best lunch boxes for keeping food hot, the thermal containers that keep food hot for hours, and a few simple ideas to make any lunch container more efficient.

Food Safety: How to Keep Food Warm in Lunch Boxes Safely

The tips below are great ways to keep the temperature of your main dish warm for hours. 

However, being warm isn’t always good enough. If you reheat food to 160+ degrees but then leave it in a lunch box for hours, it will quickly enter the Temperature Danger Zone (between 40-140 degrees F.)

The goal is to keep food above 140 degrees. Otherwise, you’re creating ideal conditions for growing bacteria and other nasties that can lead to food-borne illnesses.

If you can keep the food above 140 degrees, you can hold the food hot until lunchtime.

This is why it’s essential to have the proper containers and to use additional heating methods to help your food stay hot for as long as possible.

How to Keep Food Warm in Lunch Box for Hours

Whether packing school lunches or prepping a hot meal for your lunch break, these tips will help you enjoy a hot lunch without a microwave oven!

Choose the right type of lunch bag

Not all lunch bags are created equal. The right insulated lunch box will keep your hot food that way for hours!

Use an insulated lunch bag – Start with an insulated bag at the bare minimum. Most lunch boxes already have a thin thermal layer that helps keep the items inside either warm or cold.

These are only somewhat effective, though, and you’ll notice your warm items cooling down within a few hours.

Upgrade to a thermal lunch box – Take it to the next level and grab a thermal lunch box that really locks the heat in. Unlike thinly-lined insulated lunch bags, thermal lunch boxes are made to keep your food hot.

They include a thick pad of heat-sensitive foam. Some even have built-in stainless steel containers to keep your food piping hot.

Invest in electric lunch boxes – Welcome to the 21st century! You can now buy lunch boxes that will heat up your meal. Some even make rice! Most of these have a plug and need to be plugged in 25-30 minutes before you eat.

These make more sense for adults who can access power outlets than kids who need to plug in their lunchboxes in their classrooms. Some do have battery packs, so if you have a child with sensory needs who must eat warm food, this could be a great option.

Thermal monkey lunch bag with lunch box.

Gather the right tools to keep your lunch hot

A few tools can make any lunch bag more heat efficient. These containers are great for hot lunches, packing breakfast on the go, road trips, hikes, and more.

Get an insulated thermos – There are so many hot insulated container options that keep your food nice and hot! The best ones are made by reputable brands like Thermos.

They come in different shapes, sizes, and colors and are usually made to last a long time.

The USDA agrees that this is the best way to keep your food hot for a long time.

For best results, prime your Thermos. Boil water and add it to the container to heat up the metal walls before you add your food. Pour out the extra water before adding your reheated food.

Use glass containers – Always exercise caution giving kids glass, but those small glasslock containers are an excellent way to travel with hot food. The thick glass holds all that heat. The layers of insulation in your thermal bag will help, too.

This is a great option, especially for adults or older kids.

Invest in stainless steel – Metal containers are ideal for packing hot lunches. They’ll retain additional heat, especially when paired with an insulated lunch bag.

This is a better option for little kids because the stainless steel, unlike glass, won’t shatter if dropped. Plus, stainless steel will last a long time!

A stainless steel lunch box with chicken nuggets, cucumber flowers, sweet potato chips, apple slices and chocolate chips.

5 Quick Tips to Keep Food Warm in Lunch Box for Hours

For an additional boost of heat, try these tried-and-true tips. You likely already have the tools you need around your home or kitchen!

1. Separate hot and cold items

Nobody wants to eat a hot, sweaty cheese stick that got stuck to the outside of a soup container. Many lunch boxes have an extra side for storing hot or cold foods.

Packing multiple hot foods will also keep a higher holding temperature in the bag.

2. Go old-school with aluminum foil

Wrap your hot sandwich or other dishes with aluminum foil. The foil will work to retain the food’s heat for a longer time.

You can even wrap the foil-wrapped item in a tea towel or paper towels.

3. Instant hand warmers

These heat packs you use to keep your toes warm at outdoor soccer games can also help keep food warm! Since hand warmers can get up to 163 degrees F, they are a great way to add an extra layer of heat to your lunchbox.

Activate your hand warmer and place it next to the item you want to keep warm. This is great for keeping hot sandwiches or leftover pasta dishes nice and warm.

4. Try the hot water bottle trick

Any time you add an additional heat source to your portable lunch box, you will help keep food hot for longer.

For this tip, add hot water to a plastic bottle. It will continue radiating warmth for a few hours. 

If you’re already using glass containers or stainless steel ones and have a thermal lunch box, a hot water bottle will be a third line of defense to keep food toasty for hours.

5. Use a thermal gel pack

You might be used to using cold gel packs to soothe an injury, but there are also warm gel packs that you can use to keep your packed lunch warm!

They come in a variety of shapes and sizes, making it easy to find the right one for your situation. Microwave the gel pack to heat it up, and then add it to your lunch box as an additional heat source.

The best part is that these gel packs can either be microwaved or frozen. Store some in the freezer to use as a cold pack for chilled foods, and save some to heat up for warm lunches!

Pasta soup in a thermal container with a heat pack.


How do you keep food warm for hours?

There are two essential principles to understand to keep food warm for hours. You want to help your food retain as much heat as possible, and you want to add an additional heat source.

Choose a stainless steel food container or glass containers that can be heated before you add the reheated leftovers. Prime your containers by adding boiling or very hot water. The container will absorb that heat, helping it hold the temperature for longer.

You can also wrap your container in foil and/or a cloth to lock in as much heat as possible.

The best way to add more heat is to include a bottle of hot water, instant hand warmers, or microwaveable gel packs.

By keeping the food you already reheated hot, priming the container, and adding an additional heat source, you’re much more likely to have a hot lunch even hours later.

How do you keep hot food from getting soggy in lunch box?

If you want to know how to keep food warm in your lunch box without chewing on soggy bread or wilted lettuce, try separating any items that may become soggy (bread, lettuce) from the heated things.

This would look like wrapping your sandwich in foil but storing the lettuce and tomato separately. Send a container of hot taco meat, but add a pouch of flour tortillas in a cool compartment.

How do you pack hot food for school lunch?

Start by choosing an appropriate lunch box! Choose an insulated bag at the very least, or select a thermal lunch box like this thermal bento box that can hold heat for hours. Prime any stainless steel containers by filling them with hot water to hold onto extra heat. Then, fill it with your reheated food.

A thermos with chicken noodle soup and star crackers.

Add an additional heat source, like a hot water bottle or microwaveable gel pack, to keep the entire lunch box nice and warm. You can also wrap any warm dishes with aluminum foil or a thermal food cover for a reusable option.

Your kids’ days of monotonous cold lunches are over! Hopefully, these tips make it easy to learn how to keep food warm in their lunch box daily. Bon appetit!

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