What monitor response time is

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Seeing smears behind moving targets? Monitor response time is how long a pixel takes to change from one shade to another. The box prints that wait in milliseconds. A smaller number means that one change finished sooner in a lab. It is not a rank, it is not the refresh rate, and it is not how long a click takes to reach the screen.

I play on a 1080p 240 Hz and a 1440p 155 Hz monitor, driven by an RTX 5080. For full picks, see the best gaming monitors. IPS and VA are how the crystals block the backlight. That choice is why a dark scene can trail even when the millisecond looks tiny. More monitor guides.

Panels worth a look

• IPS 27” 1440p 240 Hz, 1 ms GtG on the box: LG UltraGear 27GR83Q-B. Official: 2560×1440 IPS, 1 ms (GtG) with 240 Hz, DCI-P3 95% (typ.), VESA DisplayHDR 400, G-SYNC Compatible, FreeSync Premium, HDMI 2.1 ×2, DisplayPort, height / tilt / pivot. LG US page. Amazon search for 27GR83Q-B
• OLED 27” 1440p 240 Hz, 0.03 ms on the box: LG 27GS93QE-B. Official: 27” OLED, 1440p, 240 Hz, 0.03 ms, DisplayHDR True Black 400. That number is the pixel’s own light rising and falling, not a gray-to-gray crystal move. LG US page. Amazon search for 27GS93QE-B
• The two screens I actually sit in front of: a 1080p 240 Hz and a 1440p 155 Hz monitor. I judge trails on those, not on a listing.

The short version: the millisecond is one lab transition. Watch the trail or the halo at the Hertz you play.

What to check first

Watch one edge you already know. A dark object on a dark background, then a bright edge. Change one menu step, then look again. Do it at the refresh rate you actually use. An overdrive step that looks clean at 60 Hz can grow a halo at 240 Hz.

What the millisecond measures

On an LCD, liquid crystals move to let more or less backlight through. Response time is the wait while they go from the shade they were showing to the shade the new picture asks for. A slow move reads as a smear behind the object. On an OLED the pixel’s own light rises and falls instead. The box still prints a millisecond, and you still judge the trail you can see.

Gray to gray, often written GtG, is a change between two gray levels. That is the number a gaming listing almost always means. The maker chooses which two grays. Brands do not share one pair, so one 1 ms claim and another 1 ms claim are not the same test. Treat the figure as that maker’s fastest convenient transition, not as a shared exam.

Makers usually measure from about 10 percent to 90 percent of the transition, not from a true black to a true white. The last bit of the swing is slower, and it is left off the number. The same FAQ notes that a box that says 1 ms without saying GtG or MPRT is not a number you can compare. Some reviews also print an average of many gray pairs. That average is often several milliseconds on a panel whose box still says 1. If two listings both say 1 ms GtG, they have named a headline, not a tie.

Black to white is the long swing, from as dark as the pixel goes to as bright as it goes. It is usually slower, and it is rarely the headline. A fast gray number can sit on a panel whose dark swing is the smear you notice in a night scene.

A second figure, MPRT, counts how long a moving pixel stays visibly lit. It often includes a backlight that flashes instead of staying on. A smaller MPRT is not a faster gray-to-gray time. Shortening blur by flashing the backlight is its own feature. Response time is the pixel’s change, not that flash.

The panel type still shows up in the trail. A VA panel often finishes a dark change more slowly than a bright one. That is the black smear: a dark object leaving a darker smudge on a dark background. An IPS panel usually clears that particular trail. The millisecond on the box did not measure your map. OLED skips the crystal. LG’s 27GS93QE-B prints 0.03 ms. The picture can still smear because the finished frame stays lit until the next one. That’s the other half of the story.

The gap until the next picture

Refresh rate is how often a new picture is allowed to start. The gap between those pictures is 1000 divided by the hertz. At 60 Hz the gap is about 16.7 ms. At 144 Hz it is about 6.9 ms. At 155 Hz, my 1440p screen, it is about 6.45 ms. At 240 Hz, the Overwatch screen, it is about 4.2 ms. Those are spaces on a schedule. They are not the response time.

If the pixel is still moving when the next picture starts, the old shade overlaps the new one. That overlap is the smear. A higher hertz shortens the schedule. It does not make a slow pixel finish. A 1 ms gray change can fit inside a 6.9 ms gap and still leave a darker change running long. Do not add the gap and the millisecond into one score.

Even a finished pixel stays on until the next refresh. Blur Busters calls that the sample-and-hold effect: your eyes track a moving object while the frame sits still, so the object smears across your vision. Without a strobe, MPRT is mostly that hold. Doubling Hertz and frames halves the hold. That is why 240 Hz can look cleaner than 60 Hz on the same fast panel, and why a 1 ms GtG sticker on a 60 Hz television does not look like 240 Hz. Overdrive works on GtG. It barely touches that hold.

Input lag is the other wait people fold into this number. It is the time after the PC has sent a frame, before the panel begins to show it. Response time starts as the pixels change. A 1 ms gray-to-gray figure is not a 1 ms click. Nothing here adds those waits together. FPS monitor notes is the refresh and resolution page after this one is settled.

Overdrive

Overdrive is a control in the monitor’s own menu. It pushes the pixel past the target shade so the crystals move sooner, then pulls it back. Used lightly, a trail shortens. Used hard, the pixel goes too far and the edge grows a bright or dark fringe. That fringe is the overshoot. It is the halo, also called inverse ghosting, or a corona in some reviews.

Menu names are not universal. One set says normal and extreme. Another says low and high. Some makers label the same slider Response Time, Overdrive, or a brand word. Start from the setting the monitor already uses. If a trail bothers you, raise it one step and play the same scene. If a halo appears, step it back. Two changes in one minute will not tell you which step did the work.

A trail that survives a careful step, especially a dark object on a VA panel, is the transition the box did not print. More overdrive is how that trail turns into a halo. The return window covers the rest. A listing cannot show your scene.

Test it at the Hertz you play

Overdrive is often tuned for one refresh rate. A setting that looks clean at 60 Hz in the shop can halo at 240 Hz on the same panel, because the pixel now has a shorter gap to settle in and the voltage boost is still the old one. Test each screen at its full refresh rate. Do not judge a 240 Hz panel in a 60 Hz desktop and then take that overdrive into Overwatch.

A moving test pattern is the other way to see it. Blur Busters’ UFO Test is the easiest way to see it at home: a UFO that slides, and you look for a trail or a halo behind it. Use it at the Hertz you play, with VRR off for that one check if you want the schedule fixed, then turn VRR back on and look again.

Variable refresh and overdrive

Variable refresh, G-SYNC Compatible or FreeSync on the two LGs above, lets the panel wait for a late frame instead of tearing. It does not speed the pixel. Some overdrive tables assume a fixed Hertz. When the card draws 90 frames on a 240 Hz panel, the gap is closer to 11 ms than 4.2 ms, and the same boost can overshoot. If the halo only appears when the frame rate swings, drop one overdrive step and leave VRR on if the tear is gone. VRR is not a response-time spec.

How to see it without a lab

You do not need a photodiode. You need one scene you already know.

1. Sit the way you play. I do this on my 1080p 240 Hz monitor, once in a fast fight and once on a darker map.
2. Fix Hertz, or note the VRR range.
3. Find a dark object on a dark background, and a bright edge on a light one.
4. Change one overdrive step.
5. A smear of the old color is too little. A bright or dark fringe that the picture never had is too much. Keep the step that leaves neither, or the milder smear if you have to pick.

A cable, a dirty glass, or a low-quality stream will smear for other reasons. Test a local file or the game itself. HDR, if you use it, is brightness. It is not a faster crystal. Which resolution to buy comes after this screen is already in the right spot and you still want a different picture.

What the number does not change

It does not change how many pictures a second the panel can start. A 144 Hz screen of either panel type has named the same schedule. The millisecond is how each picture settles, not how often a new one may begin.

It does not make the panel wait for a late frame. That behavior is variable refresh, and it does not speed the pixel. It does not brighten a highlight either. HDR is brightness and dimming. A fast gray-to-gray time is not a brightness spec, and a contrast ratio is not a transition time.

A number around 1 ms that you cannot see as a trail or a halo is finished. A larger number that looks clean in your scenes is also finished. Chase a smaller integer only when you can already see the smear and the menu cannot clear it without a halo.

OLED’s tiny number does not remove sample-and-hold. LCD’s 1 ms GtG does not remove a VA dark smear. I picked a 1080p 240 Hz and a 1440p 155 Hz monitor for the balance of sharpness and speed, not because one millisecond beat another. More monitor guides.

Common questions

What is monitor response time?

It's how long a pixel takes to change from one color to another, measured in milliseconds. Faster response time means less blur and smearing on moving objects.

What does 1 ms response time mean?

It means the maker measured one gray-to-gray transition at 1 ms. Other transitions, especially dark ones, can be slower, and it doesn't mean your input reaches the screen in 1 ms.

Is gray-to-gray the same as black-to-white response time?

No. Gray-to-gray measures changes between gray shades, while black-to-white is the full swing. Gaming monitors usually advertise gray-to-gray because it's faster.

Why do moving objects blur on my monitor?

The pixels are still changing when the next frame arrives. VA panels often smear dark objects, and turning up overdrive can help until you start to see halos.

What is monitor overdrive?

Overdrive is a monitor setting that pushes pixels to change faster. Too much causes bright or dark halos around moving objects, so raise overdrive one step at a time and stop before halos appear.

Is MPRT the same as response time?

No. MPRT measures how long a moving image stays visible, often using backlight strobing, while response time measures how fast pixels change color.

Does a higher refresh rate reduce ghosting?

Partly. A higher refresh rate shows new frames sooner, but if the pixels are slow, you'll still see smearing. You need fast pixels and a high refresh rate together.

How can I test my monitor's response time at home?

Use the Blur Busters UFO Test at the refresh rate you play at. Change overdrive one step at a time: trails mean too little, halos mean too much.

Does G-SYNC or FreeSync affect response time?

It can. Overdrive is often tuned for one refresh rate, so if you see trails or halos only when FPS swings, lower overdrive one step and keep variable refresh on.