These 5 Flat Irons Straighten Hair in One Pass, According to Our Testers

Dare we call them a cut above the rest.

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Photo: Instyle/Jessica Juliao

There are few beauty wins as satisfying as discovering the best flat iron for your hair to achieve sleek, glossy strands with minimal damage. That's because there's just so much to consider prior to making the purchase — temperature settings, plate material, and plate size, just to name a few.

To that end, we put 12 popular flat irons to the test on fine, thick, wavy, and textured hair. Achieving pin-straight hair in the least number of passes was the goal, but straightening ability was far from the only attribute we measured. Our testers also shared feedback on the iron's glide, its ease of use (without reading the manual first because who has time?), and its durability following a drop off the bathroom counter. The resounding favorite is Drybar's The Tress Press Straightening Iron because it straightens all hair textures in one pass, heats up quickly, and boasts an uncomplicated interface. (The pretty yellow color doesn't hurt either.)

Here are the best flat irons and hair straighteners, according to our testing.

The Winners

Best Overall: Drybar The Tress Press Straightening Iron

Drybar The Tress Press Straightening Iron
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What We Love: It straightens hair in one pass, including type 4 coily hair.
What We Don't Love: The temperature controls are very close to the plates.

Drybar is the OG when it comes to blowouts, and its reputation doesn't falter one bit with its line of hair tools meant to deliver that same professional styling experience to the home. The Tress Press is proof of that. It earned a perfect score on nearly all attributes from all of our testers.

"10/10 worth it," says our tester with fine hair. "It passed the one swipe test and did not leave much static which is rare for my ultra fine thin hair." More praise: "Love how I only needed to use one pass," says our tester with natural hair. "I also like the digital display, and the color is fun." Speaking of digital display, this feature makes it super easy to know what temperature you are styling at. The controls are easy to figure out without needing to read the manual first. In fact, none of our testers had an issue figuring out how to toggle between temperature settings, which could not be said about all of the tools tested.

The iron features an auto shut-off after one hour — rest assured, we used a stopwatch to confirm this — so you don't have to worry about forgetting to do so yourself. There's also a nine-foot swivel cord that ensures the cord never tangles or bends during use. When dropped onto a concrete floor, there wasn't a scratch left and the iron continued to perform as expected. Good news since we'd hate to chip that pretty yellow exterior. In all seriousness, nobody wants to invest in a flat iron that breaks within a few months. The best flat irons are built to last for years and years.

There's also two plate sizes to choose from, 1 inch and 1.25 inch. Reach for the latter if your hair is longer or thicker since the larger plates can help speed up your style time. Pro tip: If you like to use your flat iron to curl your hair, the larger plates will deliver a looser curl. If you prefer a tighter curl, reach for the 1 inch plates. Keep in mind, though, that the plates are titanium, which some experts will say is more damaging to the hair than ceramic because it conducts more heat. But if you don't mind using titanium plates, this iron is a true winner.

Plate Width: 1-1.25 in | Plate Type: Titanium | Max Temp: 450°F | Weight: .03 lb

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Instyle/Jessica Juliao

Best Value: Kristin Ess 3-In-One Flat Iron

Kristin Ess 3-In-One Flat Iron
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What We Love: It's priced well, pretty to look at and, most importantly, effective.
What We Don't Love: Toggling between temperatures is not intuitive.

The hair straighteners on this list run the gamut of price points, but the best bang for your buck might be Kristin Ess' adored 3-in-One Flat Iron. But affordability isn't the only reason it's won over our testers. The straightener actually works and effectively straightens all hair types during testing. Our testers also noted that the iron feels sturdy and is a feast for the eyes thanks to its sleek white and gold design. If you like your hot tools to double as vanity decor, this iron won't disappoint.

This iron offers an auto shut-off after 30 minutes, which was pretty accurate in our testing — the iron shut off at the 32-minute mark. The plates are titanium, so they deliver heat quickly and swiftly for faster styling, and the iron's ionic technology helps eliminate frizz and boost shine. As a bonus, you could use this iron to curl your hair in beach waves or more polished curls. (Here's how to curl hair with a flat iron if you want a refresher.)

There are four different temperature presets (280°F, 365°F, 400°F, 440°F) so that you can customize your style. That said, all of our testers had a hard time figuring out how to toggle between the temperatures initially. (Spoiler alert: You have to press the power button.)

Plate Width: 1.25 in | Plate Type: Titanium | Max Temp: 440°F | Weight: N/A

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Instyle/Jessica Juliao

Best Cordless: Dyson Corrale Hair Straightener

Dyson Corrale Hair Straightener
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What We Love: You can style cord-free for 30 minutes.
What We Don't Love: It is heavy.

If you've been on the fence about buying the Dyson Corrale Straightener, consider this your sign to go all the way at checkout. It's without a doubt the priciest pick on the list, but it's very much worth the splurge, according to our testers. With just one pass, it straightened each hair type without leaving behind any static. Credit that to the iron's unique copper flexing plates that allow you to grip every last inch of hair. This level of precision, combined with the straightener's advanced heat technology, means that you'll actually use less heat, which translates to less frizz and healthier, damage-free hair.

"Not only did this flat iron get my hair totally straight in one pass, but the strand felt the healthiest of any strands that I have flat ironed thus far," says our tester with type 4 hair. "I love that it's cordless as well, which makes it super mobile. The buttons are easy to use and the face is easy to read." Speaking of cordless, this flat iron can style that way for up to 30 minutes. If you're always on the go or dislike being a stone's throw away from an outlet while styling your hair, a cordless flat iron like this will feel like the best thing since sliced bread.

The downside to this flat iron is that it's quite expensive, as mentioned earlier. But if you can swing it in your budget, it will be a flat iron you can lean on for years to come. Our testers also wished that this flat iron weighed a bit less. At 1.23 pounds, it could cause some arm cramps.

Plate Width: 1 in | Plate Type: Manganese copper | Max Temp: 410°F | Weight: 1.23 lb

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Best for Fine Hair: Bio Ionic OnePass Styling Iron

Bio Ionic OnePass Styling Iron
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What We Love: It's lightweight and easy to use.
What We Don't Love: Our tester with coily hair did not find this iron effective.

The narrow ceramic plates and moisturizing heat of this Bio Ionic flat iron make it the perfect hair straightener for fine hair. Each plate is infused with a water-emitting mineral rock to keep your hair hydrated despite the fact that you're heat styling it, and the rounded edges make it easier to straighten close to your roots without leaving crease marks.

We recorded a 46-second heat-up time for this iron and it auto shuts off after one hour, as expected. The brand promises a max temp of 450°F, but our highest reading was slightly less at 440°F. All of our testers appreciated the easy-to-read digital display, and the seamless glide and hold. Our tester with fine hair was the biggest fan of them all, noting that it straightened the top and the ends of her hair really well. The middle section needed a few additional passes, but overall she was happy with the finish.

Note: If your hair is thick or very coily, we wouldn't recommend this flat iron. Our tester with 4c hair noted that it was not very effective at straightening multiple sections.

Plate Width: 1 in | Plate Type: Ceramic | Max Temp: 450°F | Weight: 0.5 lb

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Instyle/Jessica Juliao

Best for Natural Hair: T3 SinglePass Ceramic Styling Iron

T3 SinglePass Ceramic Styling Iron
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What We Love: It straightens natural hair in one pass.
What We Don't Love: There is no digital display.

When it comes to finding the best straightener for natural hair, it's important to choose a straightener that has adjustable heat settings so that you can customize the intensity. This guy has not one, not two, but five digital heat settings to choose from. That said, our testers were confused on how to toggle between those settings. (They later discovered that you need to hit the power button to do so.) They also weren't sure what temperature they were using at any given time because the iron lacks a digital display.

Still, all testers mentioned that they would buy this iron even without a digital display. "I was SO impressed!," says our tester with natural hair. "It straightened my strand in one pass and it worked very well."

The plates are also ceramic, which is a better option for natural hair. "I usually work with ceramic flat irons because they are great for delicate hair, which is what I consider natural hair to be," celebrity hairstylist Ro Morgan once told InStyle. Other perks include longer plates (to grip more hair at once), a swivel cord (for easier maneuvering), and ThermaTouch technology (to keep your fingers protected against high heat).

Plate Width: 1 in | Plate Type: Ceramic | Max Temp: 410°F | Weight: 0.88 lb

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Instyle/Jessica Juliao

Our Testing Process

There's no shortage of flat irons on the market, so we did our due diligence when determining our initial product selection of 12. We spoke to stylists to discover which flat irons they use on their clients, in addition to our own colleagues who use flat irons weekly. We also spent over 40 hours researching flat irons and reading through user feedback and comments.

Because a flat iron's performance varies based on hair type, we made sure our tester pool represented a wide range: fine, thick, wavy, and natural hair. Not surprisingly, our tester with natural hair had different feedback than our tester with fine hair. We kept that in mind when weighing the overall scores for each iron.

We asked all of our testers to grade each iron — from 1 through 5 — on a number of attributes. Outside of being able to straighten the hair well (bonus points if it could do it in one pass), our testers shared insights on the iron's glide, how easy (or not) it is to use, and how durable it is. Does it pass through the hair smoothly? Is there a digital display, and is it easy to toggle between temperature settings? Does it break, crack, or chip when dropped off the bathroom counter?

If the iron promised an automatic shut-off feature, we put that to the test as well by utilizing a stopwatch to determine the length of time. We know this is a game-changing feature for some users, so it's important to ensure it actually works. We also used a meat thermometer to test maximum temperature against what the brand promised. We disqualified any irons that measured five or more degrees above the stated maximum temperature since this could cause unnecessary damage.

Once all the data was collected, we assigned categories to the irons that performed the best.

What to Keep in Mind

For celebrity hairstylist Annagjid Taylor, finding the best hair straightener comes down to the device's shape, types of plates, and temperature settings.

Device Shape

"The way your device is built can affect how versatile it is," Taylor tells InStyle. "If the plates and outer edges are more rounded, then you can use this tool like a curling iron as well. On the other hand, straighteners with sharp edges are less multifaceted, but they can make your hair look a little bit straighter."

Plate Size

It's also important to choose a straightener based on your hair type, texture, and length. Taylor says that those with longer and thicker hair will want a straightener with wide plates to help speed up time in the mirror and reduce damage, whereas "if you have fine or over-processed hair, you'll want a straightener with narrower plates that apply less heat."

Plate Type

Titanium flat irons tend to heat up quicker than those with ceramic plates, but the strength and speed you get with titanium plates may mean sacrificing the more limited heat damage to your hair done by ceramic flat irons. Heat gets evenly distributed across ceramic plates, and they're often enhanced in one of two ways to further protect hair. When infused with tourmaline, ceramic plates create negative ions during the heat-up process, which add a conditioning layer to protect and moisturize your strands. Then you have infrared irons with ceramic plates, which not only emit negative ions but also heat hair evenly from the inside out to reduce visible damage.

Adjustable Temperature

If the thought of clamping any hot flat iron down on your colored, brittle, or otherwise damaged hair makes you cringe, look into a ceramic flat iron with a wide range of adjustable heat settings to use in tandem with your favorite heat-protecting hair products. Adjustable heat settings allow you to be in control of how hot your iron gets. If your hair is damaged, keep the temperature of the iron under 300°F.

Your Questions, Answered

What's the best way to use a flat iron?

Use a flat iron on clean, dry hair that has been brushed out and prepped with a heat protectant and/or a leave-in hair mask designed to minimize the effects of heat styling. Next, set your flat iron to the desired temperature. Linh Phan, hairstylist and founder of PhanHaus recommends sticking to a temperature between 325°F and 380°F depending on your hair texture. Generally, thicker hair types can withstand higher heat, but you don't want to overdo it. Gently glide the iron through the hair and avoid passing over the same sections multiple times.

Do flat irons damage hair?

According to Phan, flat irons do have the potential to be damaging, but only if they are used improperly or in excess. "Don't do more than four passes over any one section," Phan warns. He also recommends prepping your hair with a leave-in hair mask that works to repair hair damage. (His favorite is the K18 Leave-in Molecular Repair Hair Mask, if you're curious.) And per Phan, don't use a flat iron more than 3-4 times per week, especially if your hair is colored.

What Is InStyle Picks?

Did you notice the InStyle Picks seal of approval at the top of this story? That means our team of testers has reviewed every product on this list using a unique methodology to ensure it's really worth your time, money, and attention. We may get samples for free to try but we never promise positive (or any!) coverage in exchange. Put simply: InStyle Picks are products we love, and we've put them to the test to be sure you will too.

Want more product recommendations? From best-in-class concealer to the black pants you need for work, check out all of our InStyle Picks content.

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