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Home » School Lunch Ideas » Lunch Packing Tips

How Long Does Food Last in a Thermos

By Laura Fuentes Updated Jul 18, 2024

No ratings yet

This post explains the differences in how long food stays hot inside a thermos between the most popular brands, keeping the food hot, and selecting the right container for your needs.

While manufacturers advertise how long their brand keeps food hot, some things can help you get the most out of your container so the thermos lunch stays warm until lunchtime.

How long does a thermos keep food hot

The amount of time you need to keep food hot will depend on when you pack the lunch and heat the food and when it will be consumed. On average, most of us need to keep food hot between 6 and 7 hours.

Depending on your brand of thermos lunch container, food will stay hot for between 5 and 12 hours, so the one you purchase matters.

Check out this comparison chart by brand and price:

BrandHours HotPrice (avg)
Thermos Foogoup to 5$15
Thermos Funtainerup to 5$15
Bentgoup to 6$29
Stanley Classicup to 12$22
Stanley Heritageup to 8$24
Miraup to 5$16
Omieboxup to 4$45
Lunchbots Wideup to 5$34
Lunchbots Classicup to 6$20
Chart of thermos containers with time the keep food hot and cost.

Learn more about the features of each of those insulated containers here. 

How to keep food hot in a thermos for Lunch

The best way to keep the food hot as long as possible inside the thermos container is to heat it up properly before transferring it into the thermos. This means the food should be heated up piping hot, meaning too hot even to taste!

You can also preheat the thermos by filling it with boiling water and letting the heat warm up the metal sides and the air space between the double insulated walls.

Is it safe to keep food warm in a thermos?

Food that was cooked and stored properly makes a terrific thermos lunch. The thermos’s job is to keep the food at a safe-to-eat temperature for hours after being heated up properly and packed inside.

The time between when you warm up the food to when it will be enjoyed determines which thermos container is best for you! For this reason, most brands list an approximate time of how long it will retain the food’s temperature inside the insulated walls of the container.

How to Pack Hot and Cold Lunch Together

Packing hot and cold lunch foods inside the same lunch bag is possible by placing the hot food inside a thermos and the cold items, such as fruits and veggies, separately.

If you need to add an ice pack to keep other food items chilled, place it away from the thermos container that’s keeping the warm foods and near the cold food items.

Here is a quick video showing you how to pack hot and cold lunches the right way:

Best Hot Food Thermoses

Three things make up the best thermos container for your lunches; how much food it can hold, how long it will keep the food hot inside, and the features that make it age-appropriate for your child; meaning ease of opening and getting the food out.

Tip: if you’re packing food in a thermos for the first time, let your child try it at home first so they can open and close the container independently.

Here are 3 great performing thermoses:

stanley thermos container
Stanley Heritage
Holds 14oz (1 ¾ cups) of food, stays hot for up to 8 hours, is dishwasher safe, and has a lifetime warranty.
Appropriate for kids of all ages!
Get the Stanley Here
blue and silver thermos container
Thermos Foogo
Holds 10oz (1 ½cups) of food, stays hot for up to 5 hours, is dishwasher safe, and the rubberized lid makes it easy to open which is perfect for younger kids.
3 color options.
Check it out Here
lunchbots thermos
Lunchbots Wide Jar
Holds 16oz (2 cups) of food, stays hot for up to 6 hours, is dishwasher safe, has a large opening that makes it easy to access the food, and is a container that can grow with the child.
Available in 4 colors.
Check out the Specs
yellow and orange omie lunchbox
Omiebox
This all-in-one lunchbox has a built-in thermos that keeps food hot for up to 4 hours. This lunchbox + thermos option is perfect for younger kids and makes packing lunches a one-and-done experience. 
Available in 4 colors
Buy the Omiebox Here

You can’t go wrong with any of the options above for packing lunches. A thermos is a terrific vessel for repurposing leftovers and sending hot and cold foods for lunch! A great place to start is with these delicious thermos soup recipes.

by Laura Fuentes
onAugust 22, 2018

If you enjoyed the article, please share it with others. Thank you!

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  1. Pamela says

    August 31, 2022 at 8:17 am

    Very good information found here. I live in Georgia and Florida most of the year. Outdoor activities are super popular and we, husband and I, regularly pack our thermal jars for trips kayaking, boating, fishing, site seeing, etc. That said, we also take a backpacking Canister-style stove with us to reheat foods we’ve packed. Our tip is this: pack foods such as cooked Spaghetti, cooked Meatloaf, cooked Stuffed Green Peppers, in a thermal jar the night before. Place the jar with the food contents in the freezer (important: lid must be off) and leave it to freeze overnight until rock hard solid. Next morning put the lid on it and enjoy your day. By dinnertime the food is thawed enough to take out of the thermal jar and heat for your meal. Excellent to do this for wild camping!

    Reply
  2. mycfavisit says

    December 05, 2020 at 9:00 am

    This article is too informative. I really recommend to my friends and family.

    Reply
    • MOMables-Laura says

      December 07, 2020 at 1:27 pm

      Thank you!

      Reply
  3. Melissa says

    November 30, 2020 at 8:46 am

    Thank you!!! Appreciate your thorough information!!

    Reply
  4. Jamie says

    September 09, 2020 at 1:43 pm

    Not a mom, but thank you! This was a very helpful thing for me to read since I recently learned about food “danger zones” (I admit I’ve been living in a hole). All the other reviews would just say things like “cold”, “warm”, and “hot” but you actually gave the temperatures which is what I needed!

    Reply
    • MOMables - Laura says

      September 15, 2020 at 4:15 pm

      That’s exactly why I wrote that post! Glad you found it helpful.

      Reply
  5. Azucena says

    August 22, 2017 at 12:17 pm

    I’m new at packing school lunches and I was wondering if packing a thermos filled with hot food in a lunch bag that contains ice pack and cold snack impact the temperature of the food in the thermos?

    Reply
    • MOMables - Laura says

      August 22, 2017 at 2:52 pm

      Hi Azucena! This video is exactly what you are looking for to show you how to pack hot and cold foods in the same bag. Enjoy!

      Reply
      • Lyndsy says

        August 28, 2017 at 10:52 am

        I had the same question. Which video shows how to pack a hot thermos with an ice pack?

        Reply
        • MOMables - Laura says

          August 28, 2017 at 5:08 pm

          Lyndsy, check out this video.

          Reply
    • Mike says

      March 06, 2019 at 4:41 pm

      No it does not affect the temperature in a thermos by any noticeable amount because the vacuum in the thermos walls prevents a fast transfer of hot and cold inside or outside. That’s why the food stays hot or cold.

      Reply
  6. Jillian says

    March 07, 2017 at 1:10 pm

    Hi, I’m just wondering how exactly you preheat the thermos? (I’m specifically looking into the Stanley one)

    Reply
    • MOMables says

      March 08, 2017 at 5:35 pm

      They all really work the same. Here is a link to an older post: https://www.momables.com/how-to-warm-a-thermos/

      Reply
  7. Jan says

    February 14, 2017 at 4:31 am

    Hi,
    Helpful article. thank you.
    Would you know if when I put during lunch time a hot soup into a Thermos container (double wall stainless steel) and keep it there until the next day and reheat it in microwave, if it is safe to eat for an adult? It is a vegetable soup.
    Thank you,
    Jan

    Reply
    • Stephanie Schneller says

      February 14, 2017 at 12:06 pm

      This would not be safe. Stainless steel cannot be heated in a microwave.

      Reply
  8. Lakshmi says

    November 08, 2016 at 2:25 pm

    Thank you for this post! Your comparison of various products is very useful! I am specifically looking for an insulated container which does not have any plastic touching the food. The Lunchbots fits the bill, but the lid is a bit wide for my 4 old. Have you come across any other newer ones which don’t have plastic on the inside of the lid?

    Also, could you please share which is the drinks container you use in the video?

    Reply
    • MOMables says

      November 10, 2016 at 11:46 am

      I have not found any thermoses that do not have plastic on the lid. sorry! Here are our top lunch containers: https://www.momables.com/top-5-lunch-containers-for-school-office/ and our essentials: https://www.momables.com/back-school-lunch-essentials/
      and here are the thermoses: https://www.momables.com/top-5-thermos-containers-for-school-lunches/ I Hope this helps!

      Reply
  9. Kristin Suyanto says

    October 07, 2016 at 2:14 pm

    Hi Laura,

    Is it safe to keep baby soup for 8 hours in Thermos?
    I take my baby to the office, and she needs to eat lunch at 12pm and “dinner” at 4pm. We leave home at 8am
    She doesn’t like instant baby food and jar food :(

    Reply
  10. Suzanne Bare says

    October 05, 2016 at 6:34 pm

    Thank you for this post – it had just the answers I was looking for!!

    Reply
    • Emilie Hebert says

      October 22, 2016 at 1:34 pm

      Awesome!!

      Reply
  11. Becca says

    September 25, 2016 at 10:51 pm

    I know this posting is quite old, but I was curious to see if you had mold issues with any of your thermoses? A lot of the reviews on Amazon for the ones you recommended discussed mold issues in their reviews. Thank you so much! I appreciate you testing these products for all of us mommies!

    Reply
    • Emilie Hebert says

      September 29, 2016 at 1:10 pm

      Our team and families have never encountered any problems. As long as you wash them and dry them completely, you should be good. We’re glad you love these posts

      Reply
  12. Mo says

    September 14, 2016 at 2:21 am

    Thanks for the video. Don’t think you’re supposed to microwave the lids on those glass containers, though. I always remove mine.

    Reply
    • MOMables says

      September 23, 2016 at 1:59 am

      Hi Mo, the lid isn’t secured tightly on the container, it’s placed on top to prevent splatters.

      Reply
  13. Mary says

    January 13, 2016 at 3:56 pm

    I wanted to share this, but Facebook won’t let me. It’s flagged their security system, just FYI. Thanks for the great info.

    Reply
    • MOMables says

      January 14, 2016 at 10:07 am

      I’m sorry about that, Mary! Did you click the Facebook “share” button or try to copy and paste the link into Facebook? It might’ve just been a one-time thing, so if you want to try again go ahead! Thank you!

      Reply
  14. Tahmina Amos says

    December 16, 2015 at 8:16 pm

    Thank you so much for making this so easy for me! My son has swallowing issues and packing lunches can be difficult. I really appreciate the hard work you put into this by testing everything and sharing your info. I have no doubt that you have saved me so much time, money and frustration!!

    Reply
  15. Jessica says

    November 09, 2015 at 1:57 pm

    I just got my son the 10oz funtainer. This week my husband is on a work trip, so I have to drop off my son earlier than usual. If I am putting his food in the container around 6:15 and he eats around noon will it be safe?

    Reply
    • MOMables says

      November 14, 2015 at 11:57 am

      Funtainers are good for about 5hours, given that you heat the food as mentioned on the post.

      Reply
  16. Julie Moussot says

    September 06, 2015 at 1:20 pm

    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!

    Reply
  17. Brittany says

    August 26, 2015 at 3:38 pm

    Any suggestions on how to pack a thermos in a lunch box with cold items, such as juice box or yogurt?

    Reply
  18. Rachel says

    June 09, 2015 at 8:41 pm

    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?

    Reply
    • MOMables says

      June 10, 2015 at 5:55 pm

      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.

      Reply
  19. Karen Lynne says

    February 14, 2015 at 7:52 pm

    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?

    Reply
    • MOMables says

      February 15, 2015 at 9:43 pm

      2 years going strong. the reason the seal breaks is because people are putting it in the dishwasher. The lid should be hand washed.

      Reply
  20. Rebecca says

    December 21, 2014 at 2:47 am

    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.

    Reply
    • MOMables says

      December 21, 2014 at 7:47 pm

      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.

      Reply
      • Rebecca says

        December 27, 2014 at 12:11 am

        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 !

        Reply
  21. Connie says

    November 22, 2014 at 9:39 pm

    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.

    Reply
    • MOMables says

      November 24, 2014 at 8:56 am

      Exactly what I preach. Thanks Connie!

      Reply
  22. Stephanie says

    September 05, 2014 at 9:03 am

    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.

    Reply
  23. Rosa says

    August 22, 2014 at 1:33 am

    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.

    Reply
    • MOMables says

      August 22, 2014 at 10:03 am

      I’ve searched everywhere an there are no square/rectangular thermos containers out there. I wish!

      Reply
  24. C says

    August 17, 2014 at 11:51 pm

    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.

    Reply
    • MOMables says

      August 18, 2014 at 8:13 am

      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.

      Reply
    • Laurie says

      August 25, 2014 at 5:31 am

      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.

      Reply
  25. Anna says

    July 28, 2014 at 10:24 pm

    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.

    Reply
    • MOMables says

      July 29, 2014 at 10:34 am

      I use a thermos too. The food will still be warm.

      Reply
  26. Sunetra says

    July 14, 2014 at 6:54 pm

    Should I still use cold packs inside the lunch box while packing a hot lunch in a thermos?

    Reply
    • MOMables says

      July 15, 2014 at 12:49 pm

      Yes. a thermos keeps the temperature hot inside. the icepacks are for the rest of the food (when needed)

      Reply
  27. Erica munden says

    April 06, 2014 at 9:54 am

    Hi
    I would like to know if any one has any suggestions on a food box or something to keep food hot, I,m going to do a food service driving round before I buy a jiffy van,
    Ericaxx

    Reply
    • MOMables says

      April 06, 2014 at 11:04 am

      I’m sorry, I don’t know. perhaps you can go on amazon and look for those big delivery bags that the pizza people use?

      Reply
      • Kelly says

        August 26, 2014 at 6:47 am

        The catering company my daughter worked for used regular coolers like igloo. They heated the food in foil serving dishes and stacked them in the coolers.

        Reply
  28. Jorge says

    December 29, 2013 at 7:38 pm

    Hello,
    Does anybody has any experience using Mr. Or Ms Bento container kits?

    Reply
    • MOMables says

      December 29, 2013 at 11:27 pm

      No, I’m sorry. I prefer thermos containers or those made of stainless steel specifically for hot items

      Reply
  29. Ann Marie says

    November 03, 2013 at 6:58 am

    This may be a silly question, but his do you heat up the thermos? Is it microwave safe? The one I own has a metal interior.

    Thanks

    Reply
    • Ann Marie says

      November 03, 2013 at 7:13 am

      I did see your post on how to heat up the thermos, thanks!!

      Reply
  30. Nikki says

    October 02, 2013 at 1:30 pm

    I am looking for a good container for my husband that will hold plenty of food for him and keep it warm for quite a while. I was checking out the Stanley you shared about above and while reading reviews some people was saying that this was great at first and then lost its seal and wasn’t keeping the food hot for long, after only a month or so. I was wondering if you have experienced this at all? Thanks soo much, just found your site today (from 100 days of real food) and already love it!
    http://www.amazon.com/Stanley-17oz-Classic-Vacuum-Black/dp/B0019D7AGE/ref=lh_ni_t?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

    Reply
    • MOMables says

      October 02, 2013 at 2:28 pm

      Hi Nikki! Thanks for visiting us! I love that Stanley thermos. That’s the one my husband takes to work. The seal might of come off for other people if they wash and dry the lid in the dishwasher. I only wash the bottom of it, the top by hand. The “seal” is a rubber gasket/band and can come loose with high temperatures. I’ve had mine for over a year with 2-3x week use and no issues. :)

      Reply
  31. brittany says

    September 26, 2013 at 5:04 pm

    Why no onions??

    Reply
    • MOMables says

      September 27, 2013 at 9:35 am

      they tend to stink the lunchbox, often make other foods soggy..etc.

      Reply
  32. Amie says

    August 29, 2013 at 8:17 am

    You have mentioned heating up the thermos but most are stainless steel so can’t go in the microwave. How do you recommend heating them up properly?

    Reply
    • MOMables says

      August 29, 2013 at 11:34 am

      Amie, check this post.

      Reply
  33. Kimberly says

    August 29, 2013 at 5:43 am

    Thank you for this informative post! I love your site, and your newsletters. It is nice to follow you on Pinterest, as well, to see specific articles like this one on mornings when it seems like I need the advice the most! Your efforts for this experiment will help many, many Moms out there to pack great hot lunches! I do have one question – when I pack a Thermos with hot lunch for my kids I often don’t know what else to include with the entree. I am so used to packing items with a cold pack that I don’t know what accoutrements I can send with a hot Thermos full of, for example, ravioli with sauce. What items do you suggest?

    Reply
    • MOMables says

      August 29, 2013 at 11:47 am

      Kimberly, pack anything else you would normally send. the thermos containers don’t absorb heat or cold from the outside. I send fruit, veggies and dip, some of the bars in our recipe section… a thermos is just a container… send the same items you would normally pack in another container.

      Reply
      • Kimberly says

        September 05, 2013 at 5:30 am

        Thanks for your response! Do you still use a cold pack to keep the other foods chilled?

        Reply
        • MaryB says

          September 06, 2013 at 11:24 am

          I use a Packit for my kid’s lunches and we put the Thermos inside with the rest of the food. The food inside the Thermos stays hot just fine. We use the Funtainers.

          Reply
  34. Rashelle says

    August 28, 2013 at 10:02 pm

    So thorough, thank you for the great advice.

    Reply
  35. Debbie W says

    August 28, 2013 at 6:40 pm

    Excellent advice. I have the 10 oz. Thermos brand stainless containers plus another bigger stainless container that I don’t remember the name of. I always preheated the container by pouring boiling water in it. After dumping the hot water, I then added the hot soup. My daughter had no problems at all when she was young with this. Especially since she’s my soup kid. From when she was tiny to today, at 21, she will still eat soup before most other things.

    Reply

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  1. Lunchbox Burrito Bowls says:
    June 20, 2016 at 3:29 PM

    […] The best part about making burrito bowls for dinner is that they make great leftovers for your lunchbox!  Create a burrito bowl unique to your child’s taste, or even better, have them help. If you don’t have access to a microwave, you can layer your warmed ingredients inside a thermos.  […]

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laura fuentes momables holding a lunch bag and lunch boxes

My name is Laura Fuentes
I’m here to help you simplify school lunches with fresh ideas your kids will actually eat.

Mom of 3. Certified in Integrative Nutrition. 5x Cookbook Author.

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