Most insulated food thermoses are designed to keep food hot for 5 to 10 hours, depending on the brand, size, and how you pack them. For school lunches, I look for a container that keeps food hot from when I pack it in the morning until my kids are ready to eat. Below, I’ve compared popular thermos containers and shared what makes the biggest difference in keeping food hot.
How long does a thermos keep food hot?
If you pack lunch at 7 a.m. and your child eats at noon, you need a thermos that can keep food hot for at least 5 hours. Some containers are rated for longer than others, so it’s worth checking before you buy. Here’s how popular brands compare.
| Brand | Hours Hot (advertised) | Approx. Price |
|---|---|---|
| Thermoflask | up to 7 | $25-$30 |
| Hydrapeak | up to 10 | $20 |
| Funtainer | up to 6 | $20 |
| Lunchbots | up to 6 | $30 |
| YETI | up to 8 | $50 |
| Omiebox | up to 5 | $45 |
| Amazon Basics Thermos | up to 8 | $14 |
How to keep food hot in a thermos for lunch
The two things that make the biggest difference are heating the food thoroughly and preheating the thermos before filling it. A cold container immediately pulls heat from the food, which means lunch cools down faster. I show you exactly how to preheat a thermos so the food stays hot longer.
Is it safe to keep food warm in a thermos?
Yes, you can safely pack hot food in a thermos, but keeping it warm and keeping it at a food-safe temperature aren’t the same thing. Hot perishable foods should stay at 140F or above. How long that lasts depends on the thermos, how hot the food was when you packed it, and how long it sits before lunch.
If you’re unsure whether your container keeps food hot enough, test it at home with a food thermometer at the time your child would normally eat.
How to Pack Hot and Cold Lunch Together
When choosing a thermos for school lunches, I look at three things: how long it keeps food hot, how much food it holds, and whether my kids can open it without help.
Another option for younger kids is the OmieBox, an all-in-one lunchbox with a built-in thermos that keeps food hot for up to 4 hours. I like that you can pack a hot main dish and cold sides in separate compartments without needing multiple containers.
Best Hot Food Thermoses
When choosing a thermos for school lunches, I look at three things: how long it keeps food hot, how much food it holds, and whether my kids can open it without help. I’ve tested many containers over the years, and you can see my favorite thermos containers for kids to find one that works for your child’s age and appetite.
Still wondering what to pack?
Download my Printable Lunchbox Builder to turn the ingredients you already have into lunch ideas in minutes, or browse hundreds more kid-approved lunch recipes here.
Julie Moussot says
I have been using Thermos Foogo containers for years with good success. To pre-heat the container, I add boiling water and screw on the lid while I heat the food. Just dump the water and refill with lunch and you will be goo to go!
Brittany says
Any suggestions on how to pack a thermos in a lunch box with cold items, such as juice box or yogurt?
Rachel says
Lisa from 100 Days had a whole post about how pre-heating the thermos has no effect on how the food keeps its heat. Thoughts?
MOMables says
While I respect Lisa and her process very much, I was curious about this. I took the time to preheat and test the thermoses as shown. The temperature is clearly different. To me, it is worth taking the minute to preheat.
Karen Lynne says
Have you continued to use the Stanley thermos with success? Most of the reviews I read said they only lasted a few weeks before the seal broke. Evidently, they are now made in China, and the quality isn’t up to previous expectations. What has your experience been?
MOMables says
2 years going strong. the reason the seal breaks is because people are putting it in the dishwasher. The lid should be hand washed.
Rebecca says
Laura,
I struggle with keeping foods (other than soup) above 140 degrees from 7:15am to 12:15pm which is the time between when my sons lunch is packed and eaten. Any further advice? I’ve reheated spaghetti and marinara on the stove. I can only heat it to about a maximum of 180 degrees without burning it before putting it in a thermos preheated with boiling water. I’ve tested the temperature and after 2 hours using the funtainer thermos you recommended and it is in the neighborhood of 130 degrees which concerns me because for the remaining 3 hours it would be in the danger zone. I’m still so puzzled as to how to tackle a safe hot lunch. Thanks so much for your thoughts.
MOMables says
Rebecca, the foods we tested in our tests were heated in a microwave (sorry!) stirring often to prevent hot spots. As a mother of 3, I am less concerned with “safe temperature issues” in winter than summer. My biggest concern is where my kids’ hands have been (school bathroom… gross) rather than food that I’ve prepared at home and cooked it thoroughly the first time. Of course, you have to do what’s best for your family and I am glad you are testing this for your own precautions.
Rebecca says
Thanks so much for your additional thoughts on keeping hot lunches hot and safe Laura. I too am most concerned about clean hands at lunch time. I actually pack a mini alcohol based hand sanitizer in my son’s lunch !
Connie says
To keep lunches hot I heat food really hot, like said above. I also put boiling water in the canister to heat the container. And remove it, just before adding the food. That’s way your food doesn’t start cooling down right away from putting the food into a cold canister.
MOMables says
Exactly what I preach. Thanks Connie!
Stephanie says
I just want to say Thank You for your suggestion about keeping my child’s food hot in a thermos. I wouldn’t have thought about it. My son is so happy that he can have other foods besides PB & J or bagels.
Thank you again. Can’t wait to see what other ideas you have.
Rosa says
Do you know of any rectangular container that can keep food warm? Something that the kids can open up and eat in like a small plate? I currently use a Thermos too but the mouth of the container is small. Short of using 2 Thermoses, is there one that can keep 2 different foods warm while keeping them separate? My son does not like the sauce or meats mixed with the pasta or rice.
MOMables says
I’ve searched everywhere an there are no square/rectangular thermos containers out there. I wish!
C says
Do you keep foods besides soups warm? Weird question but my daughter loves sauteed shrimp and asked if I could pack her some in her stainless thermos. Do you think it would remain warm and safe even though it won’t be completely full? My husband is convinced that this is a horrible idea.
MOMables says
I use a thermos more often for other leftovers than just soup! A thermos is a wonderful idea. If your food was cooked to a safe temperature for dinner, reheating it and placing it in a thermos will be no problem.
Laurie says
Hey, C! Since shrimp take almost no time at all to cook completely, I’d recommend actually starting with raw shrimp in the morning. It might take an extra minute or two in the morning, but if you’ve prepped them for dinner, then they’re ready to cook.
Just make sure to hold boiling water in the thermos until ready to place the freshly cooked shrimp into it. I’ve done this myself for shrimp and seafood dishes, and haven’t had a cold. or otherwise unappetizing dish yet.
Anna says
What if my child’s lunch time isn’t until 6-7 hours after? I leave for work in the morning at 6:15 AM, dropping him off at the extended hours program. (He eats breakfast there). Lunch isn’t until after noon.
MOMables says
I use a thermos too. The food will still be warm.