Do you want to know how to keep food warm for hours in a lunch box? A container designed to keep food warm, such as an insulated food jar or thermal food jar, is an easy way to pack a warm lunch for school, childcare or work.
First published in June 2024. Updated in August 2026.
Quick answer: how do you keep food warm in a lunch box?
Use an insulated food jar, thermal lunch container or vacuum-insulated lunch box. Preheat the container with boiling water, add piping-hot food and seal it immediately. A good-quality insulated lunch box or food jar can keep food warm for up to six hours, depending on the product, the food and how it is packed.
How to keep food warm for hours in a lunch box
If you want to send the kids to school with a hot lunch or enjoy a hot lunch at work yourself, you need a lunch box that keeps food warm.
An insulated food container, insulated lunch container or thermal lunch box can keep hot food hot for up to six hours. These products are specially designed with a double-walled container. The air between the two walls is removed during manufacturing to create a vacuum, helping prevent heat from escaping and keeping the food inside hot.
For the best results
- Fill the food jar with boiling water and leave it for approximately five to ten minutes before packing.
- Heat the food until it is piping hot before transferring it into the container.
- Fill the container as much as practical, as empty space allows heat to escape more quickly.
- Seal the lid straight away and avoid opening it before lunchtime.
- Always follow the manufacturer's instructions and your school or workplace food-safety guidance.
Insulated and thermal lunch boxes that keep food warm
Here at Biome, we have insulated lunch boxes, thermal lunch containers and insulated food jars for adults and kids.
Bentgo Stainless Steel Insulated Food Container
The Bentgo Stainless Steel Insulated Food Container might be the best insulated lunch box for adults. If not the best, it is definitely high up there.
It features a 2.4 cup capacity and an extra-wide opening, so it is easy to fill, convenient to eat from and a breeze to clean. The lid is leak proof and inset with a built-in handle. It also features an easy-open valve and a stylish brushed stainless steel finish that is scratch resistant.
A practical insulated or thermal lunch box for taking hot meals to work.
Thermos Insulated Food Jars
The original and ever-popular Thermos brand has great choices for insulated jars and thermal food jars to keep lunch hot.
A reliable choice for soups, pasta, curries, rice dishes and other hot lunches.
Insulated thermal lunch boxes for kids
Omiebox Hot & Cold Bento Lunch Box
Omiebox Hot & Cold Bento Lunch Box is an insulated thermal lunch box for kids that keeps food warm for hours. It has been meticulously designed for little children and features an easy-to-open lid, a large carry handle, customisable compartments and bright, fun colours.
The thermos section holds 280ml of food and will keep contents hot for up to six hours, while the other compartments are ideal for sandwiches, veggie sticks, crackers and more.
Because Omiebox keeps food warm for so long, it is ideal for a full-day adventure, school, childcare and prep.
MontiiCo Insulated Food Jars
MontiiCo Insulated Food Jars are great for kids. These thermal food jars are compact, reusable and easy to pack with a warm lunch for school, childcare or a day out.
A convenient insulated food jar for smaller serves and little hands.
Do insulated lunch bags keep food warm?
Insulated lunch bags keep food warm much longer than a lunch bag without an insulating layer. However, they are not as effective as an insulated food container at keeping food hot.
If your goal is to keep food hot from when it is packed in the morning until it is eaten at lunchtime, use an insulated food container or thermal lunch container. You can place that inside any type of lunch bag, insulated or not.
Pairing a thermal lunch container with an insulated lunch bag can provide an additional layer of protection from changing outside temperatures.
Food that is contained in a container that is not insulated, such as a stainless steel lunch box or a glass lunch container, will stay hot in an insulated bag for a few hours, but it will start to cool more quickly than food stored in an insulated lunch box or food jar.
SoYoung Insulated Lunch Bags
If you are looking for an insulated lunch bag, SoYoung insulated lunch bags are a mindfully designed lunchbox made from raw, uncoated linen without PVC, BPA or phthalates.
They are machine washable, come with a spill-safe insert for easy cleaning and include handy carry straps and fun prints.
A reusable insulated bag for carrying food jars, lunch boxes and snacks.
Hot lunch ideas for school and work
Once you have an insulated food jar or thermal lunch container, there are plenty of easy meals you can pack beyond soup. Choose foods that reheat well, stay moist and are easy to eat with a spoon or fork.
Hot school lunch ideas
Prepare these meals ahead of time, reheat them until piping hot in the morning and transfer them straight into a preheated insulated food jar.
- Soups and stews with soft vegetables, beans, lentils or pasta
- Pasta or noodles with plenty of sauce to help prevent them drying out
- Macaroni-style dishes made with a favourite vegetable or tomato-based sauce
- Veggie-packed fried rice or pulao
- Lentils, beans or mild curry served with rice
- Warm bean and potato fillings inspired by jacket potatoes
- Soft quesadilla pieces, packed warm in a suitable insulated container
Hot work lunch ideas
A thermal food jar makes it easy to turn last night's dinner into a satisfying work lunch without relying on a microwave.
- Leftover curry, dhal, chilli or stew
- Pasta, noodles or saucy grain bowls
- Soup with bread or crackers packed separately
- Rice and beans with roasted vegetables
- Warm leftovers topped with fresh herbs, seeds or crunchy toppings at lunchtime
You could also try our healthy instant noodles. Watch our short video to see how easy they are to prepare.
For more inspiration, discover six easy vegan lunch-prep ideas in our Work Lunch Ideas for Australia.
Helpful tip: Foods with plenty of sauce or moisture generally hold their heat better than dry foods. Keep toppings such as crackers, toasted seeds, fresh herbs and crunchy vegetables separate, then add them just before eating.
Find the right insulated food jar for your lunch
Explore Biome's range of insulated food jars, thermal lunch containers and lunch boxes for school, work and days out.
Frequently asked questions about insulated and thermal lunch boxes
What is the difference between an insulated lunch box and a thermal lunch box?
The terms insulated lunch box and thermal lunch box are often used interchangeably. Both describe a lunch container designed to slow heat transfer and help food stay warm or cold for longer. Some products use vacuum insulation, while others rely on insulating materials or layers.
What is an insulated food jar?
An insulated food jar is a reusable, usually double-walled container designed to keep food hot or cold. It is sometimes also called a thermal food jar, thermos food jar or insulated lunch container.
How long will a thermal lunch box keep food hot?
A quality insulated thermal lunch box or food jar may keep food hot for up to six hours, although results vary between products. Preheating the container, packing very hot food and keeping the lid closed can help it retain heat for longer.
What is the best thermal lunch box for kids?
The best thermal lunch box for kids will be easy for them to open, appropriately sized, leak resistant and simple to clean. An integrated option such as Omiebox combines a thermal food jar with separate compartments for cold foods, while a standalone insulated food jar can be packed inside a regular lunch bag.
Can you put an insulated food jar inside a lunch bag?
Yes. An insulated food jar can be placed inside an insulated or non-insulated lunch bag. An insulated bag may provide extra protection from outside temperatures, but the food jar itself does most of the work of keeping the food hot.
Do insulated lunch bags keep food hot until lunchtime?
An insulated lunch bag may help slow heat loss, but it generally will not keep food as hot as a vacuum-insulated food jar. For a genuinely hot lunch, place the food in a suitable insulated food container before packing it inside the bag.
Can a thermal lunch container also keep food cold?
Many vacuum-insulated lunch containers can keep food cold as well as hot. Check the individual product instructions, as performance and recommended uses vary between brands and models.
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