I am a journalist with more than 20 years of experience testing and reviewing products. I’m also a regular hand warmer user, both in-pocket on my nearly daily walks around my New Jersey neighborhood, regardless of weather, and in-glove, as an avid skier.

For this guide:

• I revisited our past picks and dismissals and investigated a new category of reusable chemical hand warmers.
• I spent more than 80 hours testing 11 devices (or pairs of devices).
• I interviewed experts at the Consumer Product Safety Commission to make sure all the models we tested are safe and we were aware of potential red flags.
• In 2018, Wirecutter senior staff writer Kaitlyn Wells also tested 23 hand warmers and spoke with a vascular surgeon about the models she was testing. Her reporting still appears in some sections of this guide.
• Like all Wirecutter journalists, I review and test products with complete editorial independence. I’m never made aware of any business implications of my editorial recommendations. Read more about our editorial standards.

Anyone who’s ever wished for just a little more warmth in their winter wanderings can benefit from portable, long-lasting hand warmers.

Broadly speaking, there are two types of hand warmers: battery-powered and chemical (including disposable and reusable options).

Battery-powered hand warmers can be as heavy as a baseball and as thick as a deck of cards. Because of their size, they’re usually not great candidates for tucking in your gloves.

Instead, you keep them in your coat pocket so they’re easy to reach when you feel cold.

They use rechargeable, lithium-ion batteries to create heat, and they turn on and off with the press of a button. Rechargeable hand warmers charge from a USB port on a laptop or wall outlet, and many of them can also work as a backup battery for your phone.

This kind of hand warmer makes the most sense if you are running errands or commuting to the office and need to turn the heat on and off for short bursts during the day. They also work well at outdoor events (like holiday light shows, camping trips, or high school football games) when you need something to keep you warm and, in a pinch, charge your phone.

But rechargeable hand warmers cost more than chemical ones, they can be finicky, and they don’t always work as promised. One model we tested didn’t even break 99 °F. Others ran super hot but then died out too quickly. Most never reached their advertised run times or temperature outputs.

We didn’t see dangerous temperature spikes from any rechargeable device we tested, and an expert we interviewed, Dr. Danielle R. Bajakian, a vascular surgeon at NewYork-Presbyterian Hospital/Columbia, confirmed that they’re all generally safe to use.

On the other hand, chemical hand warmers are cheap (disposable warmers typically cost less than $1 a pair) and easy enough to find at a local pharmacy or major retailer.

Most chemical hand warmers are thin and small enough to slip into a glove. The disposable type contains a main ingredient, such as activated charcoal, iron powder, or sodium chloride, that reacts to force (shaking) or a catalyst (like air or boiling water) to release continuous heat. Once the reaction has been ignited there’s no way to stop it, so you have to let the reaction fizzle out on its own.

The newcomer on the scene is the reusable chemical hand warmer. These are gel pockets filled with sodium acetate, dissolved in water, and a small, thin metal disk. When you bend the disk back and forth, you kick off an exothermic chemical reaction in which tiny bits of metal are released into the gel, making sites for crystals to form and allowing the stored energy of the solution to release, creating heat.

Before we tested a single warmer, we dug deep into the category—scouring Reddit boards, making sure we took many use cases into account (security guards know a ton about keeping warm outside in the cold), reading product reviews and cold-weather sports forums, and generally getting smarter about the potential pitfalls and features. After surveying all the options—and eliminating any sketchy-seeming, online-only hand warmers that appeared to have no independent corporate presence to take responsibility should something go wrong—we ended up with 11 models in our test:

• Heating speed and duration: We attached sensors to each warmer and looked at how long it took each device to warm to 99 °F and how long it stayed above that temp. We took readings at one-minute intervals.
• Charging times: For those devices that were rechargeable, we drained the battery completely and then looked at how long it took each to register as fully charged. We assessed in 15-minute intervals.
• Comfort: For each device, we spent at least a day using it as intended out in the cold. We took blustery winter walks in the Jersey ’burbs and stuffed them into gloves during all-day ski sessions in New Hampshire. We subjectively assessed the relative warmth but also whether the device would be better for glove or pocket use.

Reusable chemical hand warmers are an entirely new category of hand warmers that has emerged since our last round of testing. We were eager to try them, thinking they might provide the convenience of disposable hand warmers without the waste. Both of the reusable hand warmers we tested start out as a small squishy pouch filled with colored gel and a tiny metal disk. To activate the heat, you snap the thin metal disk back and forth; this quickly releases flakes of metal that create a chemical reaction to heat up the warmer. (It’s also a very cool process to watch as the crystals spread throughout the warmer.)

In both cases, the first use was great. But to reuse the warmer, you have to first boil it in hot water for 15 to 20 minutes. (You can’t throw it in the microwave, thanks to that little metal disk.) This is a high bar for repeat use. And the ones we tested stayed warm no more than an hour, whereas our picks stayed warm for at least five times that long.

The rechargeable Zippo HeatBank 9s Plus Rechargeable Hand Warmer is our favorite hand warmer.

First and foremost, it’s powerful and long-lasting. The Zippo HeatBank gets hot fast in just 12 minutes, faster than many of the other warmers we tested. At its highest setting, it reached a top temperature of 107 °F and stayed above 99 °F for 5 hours and 40 minutes—the second longest in our testing pool (though short of the nine hours advertised).

It’s very adjustable. It has six settings—more than any other heaters we tested. Use the lowest setting if you want to hold it in your bare hands, or use a higher setting to make your entire pocket toasty. You can also choose between one- or two-sided heat.

It’s easy to use. The small display window clearly indicates its heat level, when it’s ready for a new charge (achieved with the included Micro-USB cable), and when the device is done charging.

It’s more than just a hand warmer. The hand warmer has two USB-A ports that you can use to charge your phone or any other compatible device, and it also has a powerful built-in mini flashlight. This would be a great device to tuck into your backpack, a car’s glove compartment, or a camping or emergency kit.

It’ll fit in a jacket pocket. Measuring 5 by 2.5 inches, the Zippo HeatBank definitely won’t fit in, say, your ski glove, but it has a handy hole at the bottom of the device that you can attach to a cord or a carabiner.

Flaws but not dealbreakers

The biggest flaw is its cost. A single unit costs about $35; if you want one in each pocket, you’re spending $70.

It takes about two hours to recharge. The Zippo HeatBank takes longer to recharge than some of the other rechargeables we tested (though about the same as our budget pick). You need to plan ahead if you think you might need it, or get in the habit of recharging it as soon as you get home from an outing.

If you’re looking to save money and don’t need the bells and whistles that come with our top pick, we recommend the Ocoopa UT3 Lite.

The price is right. This pair of hand warmers costs $30, making it much cheaper than our top pick and many of the other rechargeable heaters in our testing.

These heaters are sold as a pair. This means you have one for each hand or pocket from the get-go, without having to think about it.

They’re effective, though not as powerful as our top pick. At their highest heating level, they get up to 104 °F, and it took them a reasonable 26 minutes to get past 99 °F. This is more than double the time it takes the Zippo HeatBank to heat up, but it was about in the middle of the pack in terms of the other rechargeable devices we tested. They maintained their heat above 99 °F for 5 hours and 20 minutes—20 minutes less than our top pick.

They’re adjustable—again, not as much as our top pick. These heaters have three heating levels and are comfortable against bare skin at the lowest level, though they’re best suited for pocket rather than glove use. It’s possible to fit them inside a roomy mitten—each one measures just shy of 3.5 by 2 inches—but that’s probably not how you’d feel most comfortable using them.

They share a charging cable. The Ocoopa UT3 Lite warmers come with a forked USB-C charging cable, meaning they require only one USB power slot. Recharging takes 2 hours (like the Zippo HeatBank).

Flaws but not dealbreakers

They’re not as easy to use as our top pick. Although changing the heating levels on the hand warmers is simple—you click the half-moon button at the top of the heater—it is really hard to see the little indicator lights to know where you’ve landed. I literally had to cup my hand around the device to create my own darkness in order to (kind of) see. At night, it was less of an issue, but during the day, they were impossible to see.

If you want a pair of hand warmers that you can tuck into your gloves, it’s hard to beat the HotHands Hand Warmers.

They perform nearly as well as our rechargeable picks. These things get hot reasonably quickly (within 30 minutes). Although the package claims they stay hot up to 10 hours, we found the reality was closer to a solid five and a half—still very respectable. Possibly because they’re made to go inside your glove, they don’t get as hot as our rechargeable picks, topping out at 102 °F.

They’re very easy to find. Skiers and other outdoor sports enthusiasts will recognize this model, which looks like an oversize tea bag, from most ski lodge counters, sports stores, and even many drugstores and big-box stores.

They’re affordable. If you buy the warmers in bulk, they cost about 75¢ per pair. (A full box is about $30 for 40 pairs.)

They’re easy to use. Each HotHands package comes with two discreetly wrapped warmers—you can use them one at a time or open them simultaneously to put one in each hand or pocket. You can squish one into the palm of your hand before you put on your glove, or zip one into a mitten pocket designed for hand heaters. Drop them into the snow while you’re adjusting things after vacating the chairlift? No worries, brush them off and pop them right back in your glove or pocket.

Flaws but not dealbreakers

The big one is environmental. These are meant to be disposable. Once they’ve cooled down, your only choice is to chuck them and open a new pair.

You can’t calibrate the heat. The warmers have just one level of heat—full-on—and some of our testers found them a little too hot for bare hands. (Because they’re so small and malleable, it’s possible to move them around in your glove and reduce the skin contact.)

This is not a comprehensive list of everything we tested in all previous iterations of this guide, just what’s still available.

Disposable

Grabber Hand Warmers: These performed nearly identically to our disposable pick. They were just slightly more expensive.

Ignik Hand Warmers: These warmers also come in pairs, but they’re not individually wrapped. When you open the pack, you start the clock on both warmers. With our pick (and the Grabber model), you can opt to open just one warmer in the pair.

Rechargeable/reusable

Ravean Hand Warmer: The cork design was beautiful, but this warmer was too hot to hold in a bare hand, and it stayed hot for two hours less (3 hours and 20 minutes total) than our top pick.

Survival Frog QuickHeat Pro HandWarmer Rechargeable Portable Power Bank: The Survival Frog works as a power bank, but only while the Frog is itself being charged—which defeats the purpose of being an on-the-go charger. None of the settings were comfortable for bare hands, and it’s one of the most expensive devices we tested.

Ocoopa HeatCube: Cheaper than some of the other all-in-one heaters, this rectangular device did much better in terms of charging time but way worse in terms of heat-up time, and it topped out at 101 °F. The indicator lights were also hard to see.

Ocoopa UT2s Mini: We couldn’t get this pair of warmers above 97 °F in our testing, which was an automatic dealbreaker.

HotSnapZ Reusable Hand Warmers: Once we wiggled the metal disk to initiate the warm-up, these warmers got hot very quickly, in 9 minutes flat. They topped out at over 106 °F, but they stayed above 99 °F for only an hour.

Stansport Reusable Hand Warmers: Although these heated up quickly (8 minutes to get above 99 °F), these didn’t last as long as the HotSnapZ warmers, staying above 99 °F for only 33 minutes.

Hand warmers are meant to warm your hands without burning your skin, but yours may feel uncomfortably hot when you first turn it on. That’s because you’re touching a heat source that’s warmer than your body (like when you sit in a hot tub after swimming in a pool); after a minute or two the heat should feel pleasant against your skin.

Danielle R. Bajakian, a vascular surgeon with NewYork-Presbyterian Hospital/Columbia, said rechargeable hand warmers are safe for most people to use. “I don’t really see a downside to it,” she said. “They’re not going to be against somebody’s skin for prolonged periods of time since they’re designed to be in the pocket.” She recommends following the operating instructions and disposing of the device (see below) if the battery ever leaks. And to ensure that a rechargeable model warms you up quickly, look for one that’s flatter and has a larger surface area so that it heats a more uniform area of skin.

As for the ideal temperature, that depends on the person. “A device that stays around 110 °F to 120 °F and not above that is the safest way to go. For kids, I would aim even lower around the 100 °F mark,” Bajakian added.

If you have an underlying condition, such as diabetes, a nerve injury, or Raynaud’s phenomenon (decreased blood flow causing your fingers or toes to change colors and feel numb in response to the cold), you should be extra vigilant when using these devices so that you don’t get burned.

As always, with medical matters, we recommend checking with your own health-care provider to be sure hand warmers are right for you.

The Consumer Product Safety Commission recommends the following precautions for battery-powered hand warmers:

• Look for products certified by an accredited test lab, such as UL Solutions, Intertek, or CSA Group.
• Always follow the manufacturer’s instructions for charging with the supplied or recommended charging cables and power supplies.
• Charge in an open area, not on soft furnishings, where the device can be observed for problems.
• Disconnect power when a charge cycle is complete; do not leave the device plugged in.
• Do not charge it overnight, in sleeping areas, or by points of egress.
• Store batteries and devices away from areas of egress and keep away from excessive heat or open flames.
• If you notice signs of problems, such as swelling of the warmer enclosure or excessive heating, immediately discontinue use and dispose of in accordance with local requirements—don’t just drop it off at a retail recycling location.
• There may be warnings for possible burn hazards, especially from consumers with compromised sensitivity.

This article was edited by Christine Ryan.