If you've ever stood in front of a wall of round brushes wondering which one is yours, this round brush size guide is for you. Here's the thing I tell clients all the time: the brush matters more than the dryer. Pick the right barrel for your length and it starts doing the work for you, giving you shape and shine without the fight.
A good brush is about 90% of the reason you'll love your blowout at home. If your tools feel like hard work, you'll stop reaching for them, and honestly, who could blame you? There's a reason stylists use the same brush over and over. When you're doing seven blowouts a day, you learn fast which tools make your life harder and which ones make the whole thing feel easy. The easy one almost always gives the best result, too.
Why the size matters
Think of the barrel as the shape you're setting. A bigger barrel gives you smoothness, body and a soft bend at the ends. A smaller barrel gives you more lift at the root and a tighter curve.
A good rule of thumb: you want each section to wrap around the brush about one and a half times. If it barely makes it around once, size down. If it's winding round and round, size up.
Then think about how you like your hair to look day to day. If you love a bouncy finish with lots of curve at the ends, reach for a medium barrel. If you'd rather have something a little tighter that leans toward a relaxed, beachy wave, go skinnier and keep the brush moving down the hair as you dry. Save the up-and-back motion for when you want to build volume.
Short hair, bangs and pixies
Go small, roughly 25 to 35mm. A slim barrel gets right in at the root, which is where short hair gets its shape. It's also the one you want for curtain bangs, since it gives that swoop away from the face without turning it into a flip.
Bobs, lobs and collarbone length
This is the sweet spot for the Ibiza MB5. It smooths beautifully while leaving just enough bend to tuck the ends under or flip them out. If your hair sits anywhere between your jaw and your shoulders, this is the one.
It's the one for a boxy bob or that soft, '90s-style bob everyone's asking for. The brush gives you the gentle, full blowout that makes the look feel current, whereas if you try to get the same look with a flat iron (which so many of us reach for first), it presses the hair flat and lands you closer to early-2000s, Avril Lavigne-level straight. It's also a dream for a Scandi bob when your natural wave is doing a little too much: it mellows the wave without ironing out all the movement.
Shoulder length to long
Now you can go big, 70mm and up. The Ibiza MB7 70mm is our best seller for a reason: on long hair it gives you that full, glossy, just-left-the-salon movement. For very long or very thick hair, the MB5 80mm covers more hair per pass, which means less time with your arms in the air.
What about the oval brush?
Oval brushes sit somewhere between a paddle and a round. They're quicker, they smooth beautifully and they're very forgiving if you're still finding your rhythm. Richie loves the CX7 Carbonized Wood Oval for exactly that reason.
It's also beautiful on extensions, gently smoothing the lengths so they blend seamlessly with your own hair. And it earns double points for scalp health: a nightly brush from root to tip spreads your natural oils down the length of your hair. Between that, smoothing a blowout, softening a wave and getting a slick-back just right, it's the hardest-working brush you'll own.
Why we reach for boar bristle
Our Ibiza round brushes are natural boar bristle, handcrafted in Spain. The bristles grip the hair gently and create tension without snagging, which is what makes a blowout smooth and shiny instead of just dry. It's also why a good brush lasts years, not seasons.
Finding yours
Start with your length, then think about what you want more of. Body and polish, size up. Lift and bend, size down. And if you're between two, choose the bigger one. It's easier to add shape than to take it away.
Next month I'll walk you through the full blowout, start to finish. Until then, find the barrel that suits you and let it do some of the heavy lifting.
Kristen Patterson is the founder of Private Studio and a stylist in the collective. Meet Kristen.
