We Found the 3 Best Food Thermoses to Upgrade Your Lunch Game

Ever heard of the “temperature danger zone?” It’s the balmy span between 40°F and 140°F that creates the ideal conditions for bacteria to multiply and spread rapidly in food. It’s great when it happens in controlled environments, like when you’re fermenting something, but not so much for your leftover beef stew. If left unchecked, harmful organisms (think Salmonella or E. coli) can grow to unsafe levels, which can make you sick. To keep our food safe, the USDA (and every other food safety organization) suggests keeping cold food below 40°F and hot food above 140°F and avoiding perishables that have been sitting out at room temperature for more than two hours. But what if you need to take a meal on the go and don’t have access to refrigeration or a heat source? That’s where a food thermos comes in.

Food thermoses (a.k.a. insulated food jars) are typically made with two (or more) layers of stainless steel that form the interior and exterior walls. Between these walls is a vacuum seal, which minimizes heat exchange and helps keep the thermos’s contents hot or cold for longer. A well-made insulated container can help maintain temperatures for several hours, which makes them perfect for packing a bite to eat for work or school or while traveling or hiking. 

To find the best insulated food jars, we tested a couple we already loved alongside a group of new and notable competitors. Our full lineup consisted of 14 thermoses between $15 and $50. Most models advertised their multiple layers of insulation, how many hours they could keep things hot or cold, and how leakproof they were, so we put them to the test to see how they performed in real-world conditions. We analyzed each model’s ability to retain heat and stay drip-free, as well as how easy they were to clean and if they could withstand a drop (or three) onto a concrete sidewalk. Our three favorite food thermoses were convenient and reliable lunchtime sidekicks, no matter where we took them.

The Winners, at a Glance

The Best Overall Food Thermos

Simple Modern Provision Food Jar

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The Simple Modern food jar had a straightforward design that made it super easy to clean, fill, and eat from. Its tall shape also meant that it was one of the best at maintaining temperatures (it kept soup hot for five hours in our test, which no other model beat). It was one of the most affordable options we tested, plus it scored the best in our durability test.

The Best Classic Food Thermos

Thermos Stainless King Food Jar

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After a century of making insulated food and drink containers, the iconic Thermos brand is (unsurprisingly) still one of the best on the market. We liked this one because it had excellent heat retention, was completely dishwasher-safe, and came with a surprisingly sturdy fold-up stainless steel spoon that nested inside the bowl-style lid.

The Best Food Thermos with a Large(r) Capacity

Stanley Adventure Vacuum Food Jar

View On Amazon $33 View On Stanley1913.com View On Cabelas.com

Three of the models we tested could hold over 16 ounces; of them, the Stanley jar was the only one that kept its contents hot for more than two hours (its soup stayed above 140°F for almost double that time during our test). It could carry up to 18 ounces, plus it included a conveniently attached spork, a lid that doubles as a bowl, and a separate dry compartment for toppings or snacks.

The Tests

• Heat Retention Test: We poured a generous portion (10 fluid ounces) of boiling chicken noodle soup into each thermos to determine how long it could keep a serving of food hot. We measured the temperature of the soup inside every hour until it cooled to below 140°F. Note: we did this test at altitude in Denver, so our boiling temperature to start was 202°F rather than 212°F. 
• Cold Retention Test: We scooped six ounces of chilled egg salad into each model and temped it every hour until it warmed to 40°F or above. 
• Leak Test: We filled each model to its stated capacity with water and shook it over a large piece of paper to see if any liquid escaped.
• Durability Test (Winners-Only): We filled each of the highest-performing models with water, dropped them onto a sidewalk from waist height three times, and noted if any damage occurred. 
• Cleaning and Usability Tests: Throughout testing, we evaluated how convenient each thermos was to fill and if the lid was easy to open and close. We also hand-washed each model several times, removing the gaskets to wash separately if possible. Parts that were dishwasher-safe were cleaned that way after the cold retention test. Afterward, we inspected all of the food thermoses for lingering odors or staining.

What We Learned

Size and Shape Had the Biggest Impact on Heat Retention

The capacities of the models we tested ranged from 10 ounces (for the kid-focused Thermos FUNtainer Food Jar) up to 20 ounces (for the Hydro Flask Food Jar). They also came in two general shapes: short and wide or tall and narrow. Although they were easier to fill and eat from, wide thermoses tended to be bigger and left a lot of space when loaded with single portions of soup or egg salad. Their broad interiors also created more surface area for the food inside, which allowed for quick heat dissipation within the thermos itself. This led to a steep temperature drop-off, especially in the first hour of our retention tests. 

The Bentgo Stainless Insulated Food Container, for example, could hold 19 ounces and had the largest diameter of the lineup (over five inches). It only kept soup hot in our heat retention test for a little over an hour. The Hydro Flask and Miir Food Canister (four-and-a-quarter inches and four inches in diameter, respectively) suffered similar fates, although they lasted another hour. Comparatively, the Simple Modern Provision Food Jar, Thermos Stainless King Food Jar, and Zojirushi Stainless Steel Food Jar had 16-ounce capacities (except the Zojirushi, which held 12 ounces) and diameters between three-and-a-quarter and three-and-three-quarters inches. All three kept the soup above 140°F until the five-hour mark. The only thermos in our lineup that held more than 16 ounces and kept the soup hot for over three hours was the Stanley Adventure Stainless Steel All-in-One Food Jar. It had the same diameter as the Thermos Stainless King but was almost two inches taller.

Cold Retention Wasn’t Great

None of the thermoses kept the egg salad below 40°F for more than two hours, but it wasn’t necessarily because of a flaw in their insulation (although size and shape did play a part, just like in the heat retention test). To understand this, let’s consider the temperature ranges of food safety. When we heat soup, for example, we usually warm it to at least a simmer (around 200°F). It can cool by 60°F before it becomes a bacterial haven. Refrigerated food, on the other hand, must be held below 40°F but above 32°F lest it get icy. Even if food is nearly frozen, it only has about an 8°F window before it enters danger zone territory.

Realistically, though, most fridge-cold food is closer to 40°F than it is to 32°F, especially for items stored toward the front of the refrigerator. When we first started the cold retention test, we found that our egg salad—which had been chilled overnight—was a consistent 38°F throughout. We stashed the salad in the freezer for about 10 minutes to chill it down to 34°F before starting, although extra steps like that may not be convenient when packing lunches on busy mornings. Many manufacturers also suggested that their thermoses be pre-filled with cold water and allowed to sit for 10 minutes to help cold retention (the same thing goes for hot water and heat retention), or stored in the refrigerator overnight. Users could also add a few ice cubes to the jar, or put their food in after it has been frozen (since none of the thermoses we tested were freezer-safe themselves). 

Ultimately, it is also important to consider that food doesn’t become immediately unsafe when it enters the danger zone. The USDA allows for one to two hours for food to sit at room temperature before it needs to be re-chilled or discarded. While using thermoses for cold food is a little trickier than for hot, they can still be used to buy some extra time.

Large, Removable Gaskets Were Easiest to Clean

Most of the thermoses were relatively easy to clean by hand. Even the ones with the narrowest openings could still fit a sponge inside, and there were no signs of staining on the metal interiors during our testing. Over time, though, the soft gaskets in the lids could become prone to staining or pick up odors or gunk. All of the insulated jars we tested had removable seals that could be washed separately, but we particularly liked the Hydro Flask’s red silicone one, which was broad enough that it could be put into the dishwasher apart from the lid without us fearing it would get lost or destroyed (a missing or misshapen gasket can lead to leaking and reduced insulation power). If the thermos had an exposed pressure release gasket, we also evaluated those. Most were easy to remove and replace except for Bentgo’s, which we struggled with for several minutes before we got it back in.

The Criteria: What to Look for in a Food Thermos

A great thermos should be easy to use, convenient to carry, and maintain heat for several hours. Look for an insulated jar that matches up with your usual portion size (we liked 16-ounce models, which performed well with 10 ounces of soup but also allowed enough space for multi-component meals). For the best temperature retention, look for a thermos that is tall and narrow versus short and wide. A textured or handled lid can help make it easier to open, especially when pressure builds up inside from hot contents (although we did not experience any stuck-on lids during our testing). The lid should be leakproof and have a thick, easily removable gasket for cleaning. We gave thermoses bonus points for being partially or fully dishwasher-safe, but most models recommend handwashing anyway to maintain the look and performance of the thermos over its lifetime.

The Best Food Thermoses

The Best Overall Food Thermos

Simple Modern Provision Food Jar

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What we liked: The Simple Modern Provision Food Jar was a no-frills model that stood out because of its reliable temperature retention. It kept our portion of chicken noodle soup hot for five hours and the egg salad cold for almost two. Its handled lid made it convenient to carry and easy to open. The gasket inside the cap was quick to remove and replace when needed for cleaning, plus the whole thermos could be washed on the top rack of the dishwasher (although handwashing is recommended). Its durability was the cherry on top of this impressive model: it got a few scratches and the paint chipped a little after being dropped repeatedly on the sidewalk, but no major dents.

What we didn’t like: This model was the top performer in heat retention the last time we evaluated food thermoses, but it failed the leak test. A few online customer reviews also mention leaking, which could be caused by a faulty or misaligned gasket. We didn’t experience any unexpected drips this time (even when we retested it after dropping it on concrete), but it may be something to watch for.

Key Specs

• Capacity: 16 ounces
• Weight (empty): 11.3 ounces
• Height: 7.25 inches
• Width: 3.25 inches
• Opening diameter: 3 inches
• Materials: 18/8 stainless steel and plastic
• Accessories: None
• Other available sizes: Simple Modern also makes 12-ounce models.

The Best Classic Food Thermos

Thermos Stainless King Food Jar

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What we liked: Thermos originally set the standard for insulated food and beverage containers, so much so that its name became the generic term for the whole category. This model proved the brand’s enduring quality by matching our overall winner’s temperature retention in both tests; it kept soup hot for five hours and egg salad cold for almost two. We liked its folding steel spoon (which felt nice and sturdy, especially compared to the Thermos FUNtainer’s bendy plastic one).

What we didn’t like: This model had a relatively narrow mouth opening that made filling difficult, especially when ladling in soup. The specific jar we tested came with a small dent in its side, and it got several more dings (plus some scratches in the paint) when dropped during the durability test.

Key Specs

• Capacity: 16 ounces
• Weight (empty): 12.8 ounces
• Height: 5.5 inches
• Width: 3.75 inches
• Opening diameter: 2.75 inches
• Materials: Stainless steel and plastic
• Other available sizes: There is a 24-ounce option in the same Stainless Steel King series, as well as food jars with capacities ranging from 10 to 47 ounces in Thermos’s other lines.
• Accessories: This Thermos included a foldable stainless steel spoon (which nested into the stopper) and a lid cover that could be used as a cup or bowl.

The Best Food Thermos with a Large(r) Capacity

Stanley Adventure Vacuum Food Jar

View On Amazon $33 View On Stanley1913.com View On Cabelas.com

What we liked: This Stanley was our overall top pick in our previous round of testing, and we loved it again this time. It had the most extra perks of any model, namely a sizeable lid cover (which doubled as a bowl), an attachable spork, and a separate container in the stopper to store things like oyster crackers, tortilla chips, or a small snack. It kept our 10 ounces of soup hot for almost four hours (impressive, considering it was only about half-full) and kept the egg salad cold for nearly two. While it didn’t retain heat quite as well as our other two with the portions we used, we’d recommend it to people who have bigger appetites or usually pack multi-component meals (like rice, chicken, and vegetables) since it will maintain temperatures even better when it is fuller.

What we didn’t like: It was convenient that the spork attached to the side of the thermos, but its surface was left exposed there, which didn’t feel super hygienic. The jar and lid also dented and scratched more than our other winners during the durability test, perhaps because it was the heaviest model of the lineup. The insulated body was not dishwasher-safe, although the rest of the parts were.

Key Specs

• Capacity: 18 ounces
• Weight (empty): 18.6 ounces
• Height: 7 inches
• Width: 3.75 inches (4.25 with the spork holder)
• Opening diameter: 3.25 inches
• Materials: 18/8 stainless steel and plastic (BPA-free)
• Other available sizes: While this specific model does not come in different sizes, Stanley produces other insulated food jars that range from 14 to 36 ounces.
• Accessories: This thermos included a plastic spork, which attaches to the jar's side and a lid cover that could double as a cup or bowl. It also had a storage compartment in the stopper that could hold a few tablespoons of dry toppings (like granola, nuts, or crackers).
• Cleaning and care: All parts except the vacuum-insulated body were top-rack dishwasher safe. Avoid abrasive cleansers or scrubbers as well as bleach or chlorine-containing detergents (which can corrode the steel). The seal gasket was also removable for cleaning.
  

The Competition

• S’well Eats Insulated Stainless Steel Bowl: This model was one of the top picks the last time we tested food thermoses, and it was a high-performer again this round. It had good heat retention, plus it came with a microwave- and freezer-safe inner bowl that was easy to fill and eat out of. Unfortunately, the removable bowl significantly lowered the capacity of the thermos (it could only hold about a cup, half of what the thermos could hold without it). The outer body acquired some major dents during the durability tests, which could influence its ability to stay insulated over time if the vacuum seal was compromised. It was also the priciest model in our lineup.
• Zojirushi Stainless Steel Food Jar: This model had impressive insulation (it kept chicken noodle soup hot for five hours), but it had a fairly narrow mouth and was the only model that failed the leak test because it dripped from its pressure-release gasket when shaken.
• Thermos FUNtainer Food Jar: This compact jar had the smallest capacity (10 ounces) and came in fun, kid-friendly designs. It didn’t perform quite as well as the other Thermos in our soup test, though, and the plastic version of the foldup spoon felt flimsy. 
• Bentgo Stainless Insulated Food Container: The Bentgo container could hold up to 19 ounces, which left a lot of space inside during our tests. It could only keep our single portion of soup hot for two hours, the shortest time of any model.
• Hydro Flask Food Jar: This thermos held up to 20 ounces, the largest capacity of the lineup. Since it wasn’t as wide as the Bentgo, it performed slightly better in the hot and cold tests, although not by much. We particularly liked the gasket in its lid, though, which was easy to take in and out—plus, it was sturdy enough to wash separately from the lid in the dishwasher.
• Miir Food Canister: This model showed lackluster results in the temperature retention tests (it kept soup hot for less than three hours and egg salad cold for less than one). The canister also came with a cup that nested inside the main insulated body, but we questioned its usefulness since it was prone to getting liquid inside it whenever the jar was tilted.
• Goodful Vacuum Sealed Insulated Food Jar: The Goodful jar was similar in design to the Simple Modern one, but it wasn’t dishwasher safe and didn’t hold temperatures as well.
• MAXSO 17oz Thermos Hot Food Container: While this container was a winner in previous testing, it’s no longer available. 
• Mira 17 oz: The Mira 17 oz ranked toward the bottom of heat and cold retention in our previous tests. The mechanism holding the foldable spoon in place was faulty, and the spoon clattered to the ground each time the lid was removed.
• Thermos Guardian 18 oz: The Thermos Guardian 18 oz was disqualified from our previous testing after the first round. The seal on the lid was so tight, we couldn’t get it off. 
• Chillys Bottles 16 oz: This stainless steel food pot was sleek and attractive, but lost points in our last testing because it dented easily when dropped.

FAQs

What temperatures should food stay between to be safe?

The range between 40°F and 140°F is often called the “temperature danger zone” because it is the span in which bacteria can quickly multiply and spread throughout food. For that reason, cold food should be kept at 39°F or below, and hot food should stay above 140°F. If it needs to be chilled, it should be done quickly to minimize the time the food spends in the danger zone. The USDA recommends discarding any food that has been within this zone for two hours or more (or after one hour if the temperature is 90°F or above).

How long can a food thermos keep food warm?

How long a food thermos can keep its contents warm depends on its shape, how hot the food is going in, how full the thermos is, and the ambient temperature surrounding it. Our favorite models kept a 10-ounce portion of soup above 140°F for about five hours. To get the best heat retention from your insulated food jar, most manufacturers suggest filling it with boiling water to let it preheat, then dumping out the water and filling it with hot food. The same can be done with ice water for cold food. We recommend using a thermos about the same size as your usual portion, as partially empty containers don’t maintain heat as well as full ones.

Can you use a food thermos to keep foods cold?

Yes, to an extent. While properly insulated jars can keep their contents warm or cool, fridge-cold food is usually between 33°F and 39°F. It only has a few degrees (if that) of leeway before it enters the temperature danger zone. None of the models we tested could keep egg salad from the refrigerator under 40°F for more than two hours. The best way to compensate for this is to make the food colder to start with by adding in a couple of ice cubes or freezing the food (either for a few minutes to cool it by a couple of degrees or overnight if the food will need to stay chilled for several hours). Add the food to the thermos after it comes out of the freezer, as most insulated jars aren’t safe to go into the freezer themselves.

Can you use a drink thermos to keep food warm or cold?

Yes, drink thermoses often use the same kind of double-walled vacuum insulation as food thermoses and can be used to keep their contents hot or cold for a few hours. Because drink containers tend to have narrower openings, though, they may be slightly more challenging to fill and eat out of than wide-mouthed food jars.

Why We're the Experts

• Ashlee Redger is a freelance food writer who has been reviewing equipment for Serious Eats since 2022. 
• Before that, she interned at America’s Test Kitchen, created consumer products and restaurant menus for national brands, and developed hundreds of recipes for home cooks.
• Ashlee has written many reviews for Serious Eats, including boning knives, portable induction cooktops, steamer baskets, and more.
• We evaluated 14 highly-rated insulated food jars to find which ones offered the best convenience and highest level of performance. We used almost a gallon of chicken noodle soup and over three pounds of egg salad to test the thermoses’ ability to retain hot and cold temperatures. We also analyzed if each model could be tossed around without leaking and how durable the winning models were when dropped on a cement sidewalk.
• This was an update of a previous food thermos review. We assessed the previous top performers (including the Stanley and S’well models, which were our original top picks) alongside a few new and notable competitors.