AOC U27G4XM 27-inch 4K 160 Hz Dual-Refresh Gaming Monitor Review: Speed, Flexibility And Value

In the enthusiast market, the most shopped-for monitor category is, without a doubt, 4K, specifically in the 27- and 32-inch sizes. The density of 3840×2160 pixels in these two screen formats is, put simply, where you stop seeing the dots. This makes anything look better, be it graphics, photos, documents, videos, or games. And once you’ve experienced it, you can’t go back to QHD or FHD.

The hurdle to resolution nirvana used to be price, but today there are plenty of 4K monitors available for less than $500. But for gamers, the question of frame rates remains. Yes, you can buy a fast 4K monitor, but how much will you have to spend on an equally fast video card? Moving 8.3 million pixels at 200fps is expensive. Luckily, there is a solution – the dual-mode display.

This is a fairly new trend where you get one of the best 4K gaming monitors that can switch to FHD and double its refresh rate with the push of a button. I’ve already reviewed a number of them, and here’s AOC’s latest entry, the U27G4XM. It’s a 27-inch IPS screen with 160 Hz, 320 Hz in FHD, Adaptive-Sync, a full-array local-dimming Mini LED backlight with 1,152 zones, wide-gamut color, and DisplayHDR 1000. Let’s take a look.

AOC U27G4XM Specs

The U27G4XM maximizes the nit-to-dollar ratio with a full-array Mini LED IPS panel that has 1,152 local dimming zones. There are three different settings that reduce the black level to increase contrast. This gets the monitor closer to the broad contrast delivered by an OLED at a lower cost, and with higher brightness. DisplayHDR 1000 means a 25% window pattern will exceed 1,000 nits peak, and the U27G4XM achieves this with over 1,100 nits measured from my review sample. Black levels can go all the way down to the backlight being turned off (unmeasurable), but with local dimming on medium, I saw just over 13,000:1.

There’s plenty of color saturation that covers a measured 109% of the DCI-P3 gamut, and that’s without the benefit of Quantum Dots. The U27G4XM is reasonably accurate out of the box, but a quick calibration takes it to reference-level. And there’s a spot-on sRGB mode that’s suitable for color-critical tasks.

The dual-mode feature is a one-button affair that switches between 4K/160 Hz and FHD/320 Hz. It’s great for systems without a high-end video card. To run 160 fps at a game’s max detail level in 4K will require a GeForce RTX 4090. But you can run 320 fps in FHD with a cheaper GeForce RTX 4070 Ti Super. So, what you save on the video card will buy you the U27G4XM with a few bucks left over for a nice mouse and keyboard.

At this writing, that price is $350, which gets you terrific performance and a bright, colorful image. It also includes aiming points, sniper modes, and a frame counter. There are plenty of image modes and HDR support, with four presets for HDR10 content. You even get side USB ports, which I haven’t seen in a long time. The only things missing are LED lights and internal speakers. But you get a 3.5mm headphone jack alongside the HDMI 2.1 and DisplayPort 1.4 inputs, all of which support Display Stream Compression (DSC). On paper, the U27G4XM is an impressive package. Let’s see how it performs.

Assembly and Accessories

The U27G4XM comes in fully recyclable packaging, with molded pulp that protects the contents. The panel, upright, and base assemble without tools into a lightweight setup that fits easily on the average desktop. The accessory bundle includes IEC for the internal power supply, plus nice HDMI and DisplayPort cables.

Product 360

The U27G4XM goes for a chiseled look with flat, angular surfaces making up the back of the panel and an all-screen configuration in the front. Bits of red trim outline the stand’s fulcrum and the offset cable hole in the upright. This is unique in that it’s turned to the side, so you don’t see through it if you’re not using it. The base is cast aluminum with a wide stance and solid construction. The panel snaps on, and though the fulcrum looks large, it’s a little wobbly. It’s perfectly secure, but there is some play when you tilt or rotate the screen. Ergonomics include a 5/23-degree tilt, 20-degree swivel, a 90-degree portrait mode, and a 5.3-inch height range. If you want to use an arm, there’s a 100mm VESA mount with fasteners included.

The front bezel is thin and flush with just a small AOC logo at the bottom. The OSD is controlled by buttons rather than a joystick, a move that probably helped drop the price a tad. A tiny LED indicates power status with a soft glow. The anti-glare layer has a 3H hardness and is free of visible grain.

The input panel is up and under and features two HDMI 2.1 ports and a DisplayPort 1.4 hookup. All ports have DSC and work at full resolution and refresh. There are two USBs here, too, an upstream and a downstream. Three more downstreams grace the right side for easy access. This is a rarity nowadays, and I’m glad to see a nod to convenience from a budget display. There are no internal speakers, but you get a 3.5mm jack for headphones.

OSD Features

The U27G4XM’s OSD is controlled by a row of buttons, which, by modern standards, is a little old-school. But you get one-button access to the refresh mode switch, which is nice.

The dual-resolution feature is up first in the U27G4XM’s Game Setting menu. The easier way to do it is with the second control key, which pops up a little selector. The switch takes a few seconds once you’ve set it up in Nvidia or AMD’s control panel. Also, there are seven picture modes, Standard is the default and best. You also get shadow control to brighten up dark parts of the image, general color saturation, aiming points, sniper modes, a five-level overdrive and a frame counter.

The Picture menu has eight more image modes, which is a bit confusing since you can theoretically combine them with the Game modes for hundreds of combinations. I recommend sticking with Standard/Standard for all content. There are three gamma presets plus fixed color temps and RGB sliders. HDR gets four modes, three of which can be used as emulators for SDR content. HDR10 signals add a mode called Display HDR, which is fairly accurate for color and luminance tracking. Local Dimming gets three levels of aggressiveness. Each further lowers the black level while leaving peak brightness unchanged. Strong turns off the backlight completely under zero signal conditions. You can also choose the sRGB color space here. This mode is very accurate and can be used for critical applications. The U27G4XM also has a PIP/PBP feature for the viewing of two sources at once. The PIP window can be sized and moved.

AOC U27G4XM Calibration Settings

The U27G4XM can be used without calibration in its Standard picture mode. You can use local dimming for SDR and HDR content if you like. The medium setting increases the contrast ratio to around 13,000:1 for HDR and 1,600:1 for SDR content. I improved grayscale tracking to reference level with a few tweaks to the RGB sliders. I also noted that the sRGB mode is spot-on out of the box if you need the smaller gamut. The native color space covers just over 109% of DCI-P3. Local dimming does not change peak brightness, only black levels, so the brightness values below work in all dimming modes.

Gaming and Hands-on

After spending time with the U27G4XM playing games and getting through some work, I found that I only had two minor complaints. The stand, while secure, has a wobbly fulcrum where the panel attaches. This isn’t a big deal except when operating the OSD, which ties into my second nitpick. I am so spoiled by joysticks that on the rare occasion I get control buttons, I am sad. I realize that this is a budget monitor and at that vocation it excels. But pressing the arrow keys while the panel jiggles about is annoying.

These things aside, the U27G4XM is close to flawless. I’ve noticed that budget 4K screens have been getting quicker with each new model I review. This is the fastest one I’ve seen to date with extremely low input lag and smooth panel response from an excellent overdrive. Though 4K tops out at a mere 160fps, it is free of blur or phasing artifacts. In-game movement is precise with instantaneous reaction to control inputs. It seems counterintuitive to pair a $350 monitor with a $1,600 video card, but the U27G4XM qualifies as a competitor’s tool. It’s a frag master for sure.

The dual-refresh feature was seamless in operation once I set it up in the Nvidia Control Panel. I had to set the options for UHD and FHD just once, 160 and 320 Hz, respectively, then it worked every time. I noted that each mode retained its HDR status, on or off. So, if I was in HDR/160 Hz and switched to 320 Hz, it wouldn’t stay in HDR mode if I hadn’t set it that way previously; no complaint, but just to make you aware. Fortunately, I was fine with running at 160 fps in 4K, so I had no real need for 320 Hz. If you have a slower video card, though, it’s a great alternative to backlight strobing, which usually brings phasing artifacts.

The image is gorgeous in both SDR and HDR. The native color gamut covers over 109% of DCI-P3, so there were always vivid hues to enjoy. When I needed the correct color space for SDR, I could reach for the very accurate sRGB option. The U27G4XM is qualified for color-critical apps.

Work tasks were accomplished with a clear and bright picture that made small fonts and graphical details easy to see. I could sit as close as I liked thanks to the U27G4XM’s 163ppi pixel density. The local dimming worked well on its medium setting. It didn’t increase the peak output, which was nice because then there was no need to change the brightness setting. Rather, it lowered the black level, so contrast was increased with no clipping of detail.

Other things of note were the U27G4XM’s USB ports, three of which are on the right side of the panel. Many budget screens forgo USB ports entirely so to find them here at all is a bonus. I also made use of the gaming aids, aiming point, sniper mode and frame counter. The only thing missing is internal speakers. I had to use headphones to hear game sounds.

Takeaway: The U27G4XM is a superlative value. For $350, you get 4K, 160 Hz, dual-refresh flexibility and a bright, colorful picture. It’s accurate out of the box and calibrates to a high standard. Video processing is top-notch with smooth response and super low input lag. Aside from the OSD buttons and the stand wobble, I have no complaints.

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To compare the U27G4XM’s performance, I’ve rounded up dual- and single-refresh 4K 27-inch monitors. The dual models are Titan Army’s P2712V, Acer’s XB273K V5, and ViewSonic’s VX2730D-4K. Single-mode displays include TCL’s 27R94 and Gigabyte’s GS27U.

Pixel Response and Input Lag

Click here to read up on our pixel response and input lag testing procedures.

The monitors in the response time chart are different because it’s unfair to compare LCDs and OLEDs in this test. OLED’s black-to-white transition is much faster, which is why they are smoother at lower refresh rates. On planet LCD, the XB273U F5, a G-Sync Pulsar monitor, shares the speed crown with the ViewSonic VX2730D-4K in its 288 Hz FHD mode. The U27G4XM is a bit behind at 3.58 and 3.74 ms, respectively. Doubling the refresh rate does not halve the response time. This is with the overdrive set to medium, which is the smoothest option that doesn’t have ghosting artifacts.

In the lag test, the U27G4XM takes the win at 320 Hz with a 14ms average of 25 mouse clicks. At 160 Hz, it’s 16.5ms, which is faster than nearly every other screen, including two that are running at 320Hz. So, if you can run in 4K, you’ll have one of the quickest examples available.

Test Takeaway: The U27G4XM has an average panel response for a gaming LCD with an overdrive that removes most motion blur. It’s one of the quickest in my lag test with 14ms at 320 Hz and 16.5ms at 160 Hz. That puts it above all the other 27-inch 4K LCDs I’ve tested except for the ViewSonic VX2730D-4K at 288 Hz. It is certainly the quickest 4K monitor you can buy for $350.

Viewing Angles

The U27G4XM’s off-axis image quality is a little better than most of the IPS panels I’ve photographed. The side view has a slight red tint but no change to brightness or gamma. The top view is also a bit red with reduced brightness and gamma. This is a very shareable monitor.

Screen Uniformity

To learn how we measure screen uniformity, click here.

It’s safe to say that IPS glow is a thing of the past. Today’s panels, like the U27G4XM, show excellent uniformity with no visible issues whatsoever. My sample had no problems in any part of the screen and was uniform in all field patterns, color and neutral.

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To read about our monitor tests in-depth, please check out Display Testing Explained: How We Test PC Monitors. We cover brightness and contrast testing on page two.

Uncalibrated – Maximum Backlight Level

The U27G4XM has more than enough light output for any indoor or outdoor environment. With nearly 500 nits peak available, it could be used at a location shoot or turned down to 50 nits for dark room gameplay. The panel’s native contrast is 923.3:1, a bit below the IPS average of 1,000:1. With local dimming set to medium, it delivers around 1,600:1 for SDR content with no clipping in shadow or highlight areas.

After Calibration to 200 nits

Calibration bumps the contrast up to 989.2:1, a slight improvement. With local dimming on medium, it’s around 1,600:1. If you set it to strong, the backlight is shut off, making measurements impossible. ANSI contrast stays relatively consistent at 922.1:1, which is average for IPS panels with either full-array or edge backlights.

Test Takeaway: The U27G4XM offers effective local dimming for SDR content, which sets it apart from some other screens that only dim for HDR. It has nearly 500 nits peak available, making it good for brightly lit environments. Native contrast is just below 1,000:1, and dynamic contrast is 1,600:1 with local dimming on medium. Image depth and texture are exemplary at this price point.

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The U27G4XM ships in its Standard picture mode. In the OSD’s parlance, that’s the Standard Game Mode and Standard Eco Adjustment. There are gamut selections available and accuracy is high both before and after calibration.

Grayscale and Gamma Tracking

Our grayscale and gamma tests use Calman calibration software from Portrait Displays. We describe our grayscale and gamma tests in detail here.

The U27G4XM’s default grayscale is a tad cool, but errors barely crack the 3dE threshold, the point where they become visible. Most are below the line, so this monitor can be enjoyed right out of the box. Gamma is right on the 2.2 reference line as well, with no visible issues.

Calibration takes grayscale tracking down to a pro-level 0.42dE. It doesn’t get much better than that. Gamma gets a shade light from 50-90%, but the change is barely visible in actual content. This is excellent performance.

The sRGB gamut mode cannot be calibrated, but it has visually perfect grayscale tracking and slightly light gamma that closely tracks the 2.2 reference. It is suitable for color-critical tasks.

Comparisons

The top three screens, including the U27G4XM, are visually identical in the grayscale test. 2.40dE is a solid result. After calibration, there is no visible difference among the monitors. The U27G4XM’s 0.42dE is a standout result. In the gamma test, the range of values is fairly tight at 0.11 from smallest to largest. Overall tracking is a tad light with a 3.18% deviation representing an actual value of 2.13.

Color Gamut Accuracy

Our color gamut and volume testing use Portrait Displays’ Calman software. For details on our color gamut testing and volume calculations, click here.

The U27G4XM is a very colorful monitor with extra punch across the entire gamut triangle. The default is close to perfect with slight oversaturation and hue errors in red and green. The points track linearly, so there is no loss of detail in any part of the image. Calibration only makes a slight difference that will be hard to see in a before-and-after comparison. But it’s worth doing for the improvement in grayscale tracking. The sRGB mode is better than many pro monitors I’ve tested with an average error of just 0.80dE.

Comparisons

As impressive as the U27G4XM’s accuracy is, it is competing with some equally precise displays. 2.27dE is a great score, but others score better. Is that a difference worth paying for? Not in my opinion, especially when you consider gamut volume, which is the U27G4XM’s main advantage. Amazingly, it does not have a Quantum Dot layer, but it does a great impression of that tech with over 109% coverage of DCI-P3. You will see that in the brightest content where primary colors dominate. There is a good deal of extra red, green, and blue. The sRGB result of 97.93% is nearly ideal and qualifies the U27G4XM for critical tasks.

Test Takeaway: The U27G4XM can be enjoyed without calibration, but a few tweaks take it to reference levels. Gamma is a touch light, but color is exemplary and richly saturated. It has more coverage than the competition, which is a difference that can easily be seen. The sRGB mode is very precise with nearly perfect color and grayscale.

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Our HDR benchmarking uses Portrait Displays’ Calman software. To learn about our HDR testing, see our breakdown of how we test PC monitors.

Mini LED displays like the U27G4XM are great for HDR content thanks to their bright backlights and full array zone dimming (FALD). This monitor is rated for VESA DisplayHDR 1000, which is something rarely seen in the OLED category. The signal switch is automatic, and you get four additional picture modes.

HDR Brightness and Contrast

It’s easy to identify which screens are Mini LED in the first chart above. The U27G4XM exceeds its HDR1000 rating, reaching a peak of 1,107 nits. I measured that from a 25% window pattern, and it is extremely bright. Only the TCL is brighter. Local dimming can be used to make the contrast ratio unmeasurable at its highest setting. On medium, the ratio is 13,061.4:1, which is excellent for an IPS panel. I noted that different local dimming settings did not change the peak value, only the black level.

Grayscale, EOTF and Color

In the HDR grayscale test, the U27G4XM is slightly warm in tone from 70% brightness and higher. The error is hard to spot in content, but it would be nice to have RGB sliders available. Of the four HDR modes, Display HDR delivers the best EOTF with values a little below the reference until 60%, where it goes a bit light. These are small variations that will not negatively impact the image. The tone map transition is at 75%, which is correct for the measured white and black levels.

In the color test, the U27G4XM’s large gamut is used to full effect with general oversaturation in all colors. This gives HDR content some extra punch that isn’t strictly accurate, but it is pleasing. The BT.2020 test shows the same response with color running out at 90% red, 80% green and 95% blue. In both charts, hue targets are on point for all six colors.

Test Takeaway: The U27G4XM is a superb HDR display with bright highlights and deep shadows. The Mini LED backlight effectively increases contrast to over 13,000:1 with no penalty. Color is pleasingly oversaturated with vivid hues that deliver great impact to game and video content.

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With OLED commanding the premium market, it has driven down the prices of other premium technologies, namely 4K and Mini LED. It is now possible to buy a 27-inch 4K IPS monitor with wide-gamut color, 160 Hz, premium video processing, accurate imaging, and high brightness, and that is a clear sign of progress. The U27G4XM exemplifies that design goal for $350 and offers performance we’d have paid over $1,000 for just a few years ago. And did I mention the Mini LED backlight with 1,152 dimming zones? Yeah, it has that too. For perspective, Acer’s X27 from 2018 had 384 dimming zones, 4K, and 144 Hz for an eye-watering $2,000. Check out that review here if you’re curious.

The AOC U27G4XM is better than that Acer in every way. It has 1,152 dimming zones. It has 109% coverage of DCI-P3 color. It has 160 Hz and a 320 Hz FHD mode. It has lower input lag and better panel response – and it’s $350. That’s what eight years of progress looks like. My only complaints are that the OSD is controlled by buttons instead of a joystick, and the stand is secure but a little wobbly. But performance and image-wise, there are no flaws. For the money, I can’t fault it at all. It games with the very best and provides a bright, colorful, and accurate picture for work and play alike.

If you’re looking for an affordable 4K monitor that pairs well with budget and premium video cards alike, the AOC U27G4XM is well worth checking out.

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