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.
Pamela says
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!
mycfavisit says
This article is too informative. I really recommend to my friends and family.
MOMables-Laura says
Thank you!
Melissa says
Thank you!!! Appreciate your thorough information!!
Jamie says
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!
MOMables - Laura says
That’s exactly why I wrote that post! Glad you found it helpful.
Azucena says
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?
MOMables - Laura says
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!
Lyndsy says
I had the same question. Which video shows how to pack a hot thermos with an ice pack?
MOMables - Laura says
Lyndsy, check out this video.
Mike says
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.