The Best Food Thermos | Reviews by Wirecutter

Oct 17, 2024

By Wirecutter Staff

There’s a golden rule of the communal microwave: Thou shalt not heat up gross or smelly stuff in it.

Sadly, that rule is not always followed.

If you’re trying to avoid your lunch tasting like someone else’s salmon leftovers, consider packing your meal in a food thermos that will keep it warm.

Of course, food thermoses have uses outside of avoiding the ruination of a perfectly good lunch.

Whether you’re packing chili for lunch or oatmeal to eat after your morning commute, a good food thermos will keep hot foods at safe temperatures for hours, and they won’t leak into your bag.

Unfortunately, they’re not great at keeping cold foods at safe cold temperatures.

After comparing 22 food thermoses and testing 10, we’re confident that the Zojirushi Stainless Steel Food Jar is the best. It has excellent heat retention, is durable and easy to clean, and comes in three sizes ranging from 12 to 25 ounces.

We also recommend the 10-ounce Thermos Funtainer Food Jar for packing kids’ lunches or for people who prefer smaller portions.

This container keeps food hot for hours, and it comes apart easily for cleaning.

The 10-ounce Funtainer is durable and easy for small hands to open. Plus, it comes in lots of colors and prints.

This container keeps food hot for hours, and it comes apart easily for cleaning.

The Zojirushi Stainless Steel Food Jar kept our tomato soup above a food-safe temperature (140 °F) for a full six hours. Liquids stayed warm for even longer than the six hours the brand claims.

It easily fits in one hand, and it emerged from our drop test with no dents. And it doesn’t leak.

The four-piece lid comes apart for easier cleaning, though keeping all of the parts together is cumbersome.

The Zojirushi’s heat retention is covered by a five-year limited warranty.

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The 10-ounce Funtainer is durable and easy for small hands to open. Plus, it comes in lots of colors and prints.

The Thermos Funtainer kept food hot, didn’t break when dropped, and didn’t leak. And it was easy to clean.

With its 10-ounce size, bright colors, and lower price tag, this thermos is particularly good for kids.

It fits into small lunchboxes, though it held our soup at a food-safe temperature for only four hours (versus the Zojirushi’s six-hour run).

Thermos also offers a 30-day warranty for defective products.

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It’s been years since Wirecutter’s Anna Perling rigorously and comprehensively tested food thermoses. But this is not a category with a lot of technological innovation. We’re confident that our picks are still great.

We considered models designed for kids as well as for adults. We preferred thermoses that come in multiple sizes and colors. And we tested smaller-size options (ranging from 10 to 13.5 ounces, with a few 16- and 17-ounce sizes) when possible, since we wanted a thermos that was easily portable and would fit into our picks for the best lunch box.

A great thermos should keep foods at a food-safe temperature—below 40 °F for cold foods and above 140 °F for hot foods—for long periods of time. In our tests, we considered how long thermoses kept soup and plain bow-tie pasta warm, as well as how long they kept milk and tuna salad cold.

They shouldn’t leak or otherwise compromise their contents in transport. Thermoses are meant to hold liquidy foods like soups or stews. They shouldn’t leak. Because accidents happen, they also shouldn’t break or dent significantly when dropped.

They need to be easy to clean. Most companies recommend hand-washing thermoses to preserve their vacuum insulation, but the lids and jars should be intuitive to take apart and clean.

To test our 10 food thermoses, we heated tomato soup to a boil and added it to the thermoses, checking the temperature over six hours in two-hour increments.

We did the same with pasta. Our pasta tests, however, weren’t conclusive—it took us longer to fill the thermoses with wider bow-tie noodles after straining them than it did to ladle in boiling-hot soup, and we think the pasta likely cooled during the process.

We also tested the thermoses with cold foods, filling them first with milk and then with 4 ounces of tuna salad, both at 40 °F.

Then, because both milk and tuna rose above food-safe temperatures in all of the thermoses after just two hours, we repeated the tuna test after pre-chilling the thermoses with 40 °F ice water.

A few brands, like Thermos and Zojirushi, recommend pre-chilling thermoses, but we originally skipped this step because it’s annoying for thermos users.

But even after we pre-chilled the thermoses, after two hours none of them kept tuna within the USDA’s safe temperature guidelines.

After filling the thermoses with soup, we shook them in a backpack and held them upside down to check for leaks.

We also dropped thermoses from 4 feet onto pavement to see if they were damaged after a fall.

To see how easy models were to clean, we took them apart and hand-washed them.

This container keeps food hot for hours, and it comes apart easily for cleaning.

In our tests, the Zojirushi Stainless Steel Food Jar was one of the best at keeping soup hot. It proved durable, didn’t leak, and was quite easy to clean.

It keeps its contents hot (or cold). The 12-ounce thermos kept tomato soup above a food -afe temperature (140 °F) for a full six hours in our tests, dropping from 193 °F to 144 °F.

The only thermoses that did better were the 17-ounce Stanley Classic (larger volumes of liquid take longer to cool) and the Black and Blum Food Flask (which has an awkward strap around it).

We’ve used the Zojirushi to transport morning green smoothies, chili, soup, and oatmeal. It reliably keeps foods at nice temperatures.

To keep foods hotter for longer, we recommend preheating the thermos.

It’s durable and doesn’t leak. When shaken or held upside down in our tests, the Zojirushi didn’t leak (though none of the thermoses we tested did). The Zojirushi is also durable, surviving our drop test unscathed. Other metal jars dented upon impact.

We’ve also seen it survive trips through the dishwasher without a ding, even though Zojirushi recommends hand-washing the thermos.

And it’s easy to take apart and clean. The Zojirushi has a four-piece lid that comes apart, which allows you to deep-clean all of its crevices. We liked it better than the single-piece lids on most of the other thermoses we tested, which have hard-to-reach threads that look like they would trap gunk.

The Zojirushi also comes in a range of sizes, including 11.8-, 16.9-, and 25-ounce jars, and an array of colors, including pink, aqua blue, dark brown, cream, and stainless steel.

Plus, the heat retention of the Zojirushi is covered by a five-year limited warranty.

It’s not as great at keeping cold food cold. After just two hours, cold milk in the Zojirushi rose to 46 °F; after six hours, it was 52 °F. Tuna rose to 49 °F after two hours; after six hours, it was 63 °F.

None of the other thermoses we tested, however, did any better, even after we pre-chilled them with ice water (Zojirushi recommends filling the thermos with cold water for one to two minutes before filling it with food).

Packing the thermos in a bag or lunch box with ice packs can help foods stay cold, but ultimately we found that these thermoses are best for retaining heat.

Plain pasta also cooled more quickly in the Zojirushi, dropping from 178 °F to 82 °F over six hours, but the results were similar in all of the thermoses we tested. (Solids like pasta cool more quickly than liquids, so any thermos is most effective when used with soup, stew, oatmeal, or other liquidy foods.)

Reassembly can be difficult. Although we like that the Zojirushi’s multi-part lid is easy to clean, it’s a bit more difficult to put back together afterward. The rubber gasket is tricky to get on, and keeping track of the small four parts takes effort. Also, unlike the lids of some larger thermoses, the Zojirushi’s lid doesn’t double as a cup, so you will likely eat straight from the jar.

The pieces are easy to misplace. Anna ended up losing a small rubber stopper that plugs into the top part of the lid. This didn’t affect heat retention, but sometimes foods would leak into the thermos’s cap. So she prioritized unscrewing all of the parts of the lid to make sure she could get it really clean. Despite this minor leak due to the missing piece, the Zojirushi never leaked outside of the container itself.

The colored coating can scratch easily. We tested a jar with the stainless finish, but we have read several Amazon reviews noting that the coating on the blue, pink, and tan versions of the food jar can scratch. We’ve also found that the finish on Zojirushi’s travel mugs can develop small nicks and scuffs over time, but this wear and tear doesn’t affect performance.

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The 10-ounce Funtainer is durable and easy for small hands to open. Plus, it comes in lots of colors and prints.

In our tests, the 10-ounce Thermos Funtainer kept food hot, didn’t leak, didn’t break when dropped, and was easy to clean.

We prefer it for kids over the 12-ounce Zojirushi because it comes in an array of fun prints and colors, and the slightly smaller size will be easier for kids to use. The Funtainer also costs less, which is helpful if it gets lost and needs replacing.

The Funtainer is best for small portions. The Funtainer fits neatly into smaller lunch boxes like the L.L. Bean lunchbox we recommend for both kids and adults, and can hold a 10-ounce serving of noodles, veggie chili, or hot cereal.

But it doesn’t keep food hot for as long. Although the Funtainer kept foods hot, it didn’t do as well as the Zojirushi: after four hours, soup in the Funtainer had cooled from 193 ºF to 147 °F, and at six hours, it measured 130 °F. In comparison, the Zojirushi kept soup at a hotter 144 °F after six hours.

It’s durable and easy to open. None of the thermoses, including the Funtainer, leaked in our tests. The Funtainer's plastic lid didn’t break during our drop tests, faring much better than the competition.

The Funtainer’s lid doesn’t get slippery when wet and is also easy to twist on and off.

With its uniform, cylindrical shape, the Funtainer fits easily into all of our lunch box picks. It also comes in a variety of prints and colors that will appeal to kids of different ages (and adults can select a solid color option).

Thermos offers a 30-day warranty period for defective products.

Again, it’s not good at keeping cold foods cold. None of the thermoses we tested were able to keep cold foods at food-safe temperatures during our tests, including the Funtainer. After two hours, tuna salad that started at 40 °F rose to 49 °F; at six hours, it measured 63 °F. If you’re nervous about this, pack the thermos in a bag or lunch box with ice packs, to help foods stay colder for longer.

It doesn’t fully come apart for cleaning. The Funtainer has a removable rubber ring to seal the thermos, but since it doesn’t totally come apart, it’s a little harder to clean.

To keep foods hotter for longer, both Thermos and Zojirushi recommend preheating your thermos by filling it with hot water for five to 10 minutes before dumping it out and adding foods. You can do the same thing with ice water to pre-chill your thermos before adding cold foods.

Like most of the thermoses we looked at, the Zojirushi is not dishwasher-safe, and it needs to be hand-washed. Putting it in the dishwasher can degrade its ability to retain heat.

The Funtainer is top-rack dishwasher-safe, but Thermos still recommends hand-washing it because “harsher detergents and hot water may affect the appearance.” To clean the hard-to-reach places in the Funtainer’s lid, we recommend soaking it in warm, soapy water.

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The Thermos Stainless King 16 Ounce Food Jar with Folding Spoon kept soup hotter than most of the competition in our tests. But it has a wider girth and a bulkier, ridged shape compared with our pick, so it’s harder to hold and to fit in a lunchbox.

The Black and Blum Food Flask’s brushed steel and smooth curves are sleek, and the faux leather strap and spoon attachment charmed us. But the flask isn’t as widely available as our pick, and the strap-and-spoon contraption isn’t functional—the spoon would be exposed to germs in a bag, and the strap stains easily.

We like the affordable MIRA Lunch Food Jar, but it didn’t keep soup as hot as most of the other thermoses we tested.

The lid from IKEA’s Efterfragad Vacuum Food Container broke during testing.

We also tested the Hydro Flask Food Flask Thermos Jar, the Stanley Classic Vacuum Food Jar, the Simple Modern Rover Food Thermos, and the Contigo Stainless Steel Food Jar, all of which are now unavailable across multiple retailers.

Anna Perling wrote the original version of this guide. Abigail Bailey contributed reporting. This article was edited by Marguerite Preston and Ben Frumin.

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