When someone says a screen has a '120Hz refresh rateHow many times per second a screen redraws its image, measured in Hertz (Hz). A higher number, like 120Hz instead of 60Hz, makes scrolling and motion look smoother. More in the glossary,' they're describing how many times per second the entire image on screen gets completely redrawn. Hz, or hertz, is simply a unit for 'times per second,' the same unit used for sound frequencies and electrical currents. A 60Hz screen redraws its image 60 times every second; a 120Hz screen does it twice as often.
That number has a direct, physical effect on how motion looks. Scrolling through a list, dragging a finger across the glass, or watching something move across the screen all look measurably smoother at a higher refresh rate, because the screen is showing more intermediate steps of that motion per second rather than skipping ahead in larger jumps.
This article explains what's actually happening during each of those redraws, why higher numbers feel smoother to human eyes, and where the real trade-offs of a higher refresh rate show up, mainly in battery life.
What Actually Happens During a 'Refresh'
A screen refresh means the display updates the color and brightness value of every single pixel, even if most of the image hasn't changed since the previous refresh. This happens whether you're looking at a static photo or fast-moving video; the screen doesn't selectively redraw only the parts that changed. It redraws everything, every cycle.
The refresh rate is a property of the display hardware itself; a 120Hz screen is physically capable of 120 full updates per second, but it only actually shows new motion in each of those updates if the device is also producing new image frames fast enough to fill them.
Refresh Rate vs. Frame Rate: A Common Mix-Up
Refresh rate describes how often the screen hardware can update. Frame rate describes how many unique images per second a game, video, or app is actually generating to show. These are related but distinct, and a screen with a high refresh rate doesn't automatically mean everything on it moves more smoothly.
If content is only generated at 30 frames per second, a 120Hz screen will still just show each of those 30 unique images for a few repeated refresh cycles before the next new image is ready. The refresh rate sets the ceiling for how smooth motion could look; the frame rate determines whether it actually reaches that ceiling.
Why Higher Refresh Rates Look Smoother to Us
Human vision is very sensitive to motion, more so than to small differences in static image sharpness. When an object moves across a screen in larger jumps between frames, our eyes and brain can perceive that choppiness, sometimes described as stutter, especially during fast scrolling or quick on-screen movement.
At 120Hz, each individual step of motion between refreshes is smaller than at 60Hz, since twice as many in-between positions are shown over the same second. Smaller steps between frames make motion look more continuous and less like a series of still images flashed in sequence, which is the core reason higher refresh rates read as 'smoother.'
Touch Response Benefits Too, Not Just Visuals
Many devices with a higher refresh rate also poll the touch sensor more frequently to match, which shortens the gap between your finger moving and the screen reflecting that movement. This is part of why a 120Hz phone can feel more responsive during fast scrolling or drawing, beyond just the visual smoothness of the display itself.
This touch-sampling improvement is a separate engineering decision from the display refresh rate, though the two are frequently paired together in device designs aimed at feeling fast and fluid under your finger.
The Real Trade-off: Battery Life
Refreshing the screen more often means the display and its driving circuitry do more work every second, which draws more power. All else being equal, a screen running at 120Hz consumes more battery than the same screen running at 60Hz, particularly when showing content with a lot of on-screen motion.
This is the central trade-off behind refresh rate: smoother-looking motion costs measurably more energy, which is why refresh rate is a deliberate design choice rather than something manufacturers would simply max out without any downside.
Adaptive Refresh Rate: Getting Smoothness Without the Full Cost
Many modern screens don't run at a single fixed refresh rate all the time. Instead, they adjust dynamically, ramping up to 120Hz during fast scrolling or gaming, and dropping down to 60Hz, 30Hz, or even lower while displaying a static image like a reading app or a paused video.
This adaptive approach tries to capture the visual benefit of a high refresh rate specifically when motion is actually happening on screen, while avoiding the full battery cost of running at the highest rate constantly, even when nothing is moving.
How Refresh Rate Relates to Input Lag
Refresh rate is sometimes confused with input lag, which is the delay between an action, like a button press or finger tap, and that action visibly appearing on screen. A higher refresh rate can reduce part of this delay, since the screen has more frequent opportunities to display an updated image, but refresh rate is only one contributor to overall input lag.
Other factors, including how quickly the device's processor can generate a new frame and how the touch sensor itself samples input, also add their own delays into the chain. A high refresh rate screen paired with a slow processor can still feel less responsive than expected, which is why refresh rate alone isn't a complete measure of how fast a device will feel to use.
Refresh Rate at a Glance
| Refresh Rate | Full Screen Redraws per Second | Typical Feel |
|---|---|---|
| 60Hz | 60 | Standard, noticeable motion blur during fast scrolling |
| 90Hz | 90 | Visibly smoother scrolling than 60Hz |
| 120Hz | 120 | Very smooth motion; common on higher-end displays |
| Adaptive (variable) | Switches, e.g. 1-120 | Smooth during motion, power-saving when static |
Common Mistakes
- Assuming a higher refresh rate alone makes a video look smoother, when the video's own frame rate also has to be high enough to take advantage of it.
- Thinking refresh rate and resolution are the same thing; one is about update speed, the other is about pixel count and detail.
- Expecting a 120Hz screen to always use noticeably more battery, when adaptive refresh rate often keeps real-world power use close to a 60Hz screen during static use.
- Believing refresh rate improves image sharpness; it affects motion smoothness, not how detailed or crisp a still image looks.
Frequently Asked Questions
Can the human eye actually tell the difference above 60Hz?
Most people can perceive smoother motion up to 120Hz and sometimes beyond, especially during fast scrolling or gaming, though the difference becomes harder to notice at very high rates.
Does a higher refresh rate improve picture quality?
It improves motion smoothness specifically, not color accuracy, contrast, or sharpness, which depend on separate aspects of the display.
Why does my screen feel less smooth in some apps even on a 120Hz phone?
If the app itself isn't generating new frames fast enough, the display's higher refresh rate has nothing extra to show, so motion looks the same as on a lower refresh screen.
Is a higher refresh rate always better?
It generally improves perceived smoothness but increases power use, so the better choice depends on whether smoothness or battery life matters more for a given use.
Sources
- VESA — display standards including refresh rate and adaptive sync specifications — https://vesa.org/
- IEEE Spectrum — display technology coverage — https://spectrum.ieee.org/