Redmi K40 Series Review: Would Be Affordable Flagship Phone of 2021


Redmi released the K40 series, all of which have been upgraded. The screen, performance, and sound quality have been upgraded, but the price is still very competitive. For example, the K40 Pro equipped with Snapdragon 888 has a starting price of only $429.

Therefore, for the Redmi K40 series, the “all-series upgrade cup” is not only a marketing phrase that is convenient for consumers to understand but also a high-level summary of this series. The most common feature of the Redmi K40 and K40 Pro in the configuration is the same high-quality E4 AMOLED screen, and the high refresh rate and other screen parameters remain the same.


In terms of book parameters, both Redmi K40 and K40 Pro are equipped with a 6.67-inch Samsung E4 AMOLED direct screen. Compared with the E3 material screen released in 2019, it has a higher peak brightness, up to 1300nit, and a screen contrast of 5000000:1. This means that these two phones can still maintain a clear and visible screen display under outdoor sunlight. Therefore, whether from the data or the naked eye, the K40 dual flagships are brighter than the previous generation.

The refresh rate and touch sampling rate have also been upgraded. This screen supports a 120Hz refresh rate and the first 360Hz three-finger touch sampling rate, this parameter is even higher than the current game phones on the market, and it also makes this high refresh screen more practical. To put it simply, the 120Hz refresh rate means that the screen refreshes 120 pictures per second, making it more fluid to use, and the increase in adoption rate makes the screen handier so that the screen touch can keep up with the speed of the finger sliding. The high refresh rate screen has also become better to control, especially in games that require high-precision operations such as “Glory of the King” and “Peace Elite”. The operations such as aiming and skill casting are also more stable and accurate.

With 120Hz refresh rate + 360Hz sampling rate + current MIUI optimization, Redmi K40 and K40 Pro screens are quite pleasant to use. The desktop page-turning frame drop problem has been significantly improved, and the page-turning animation is very smooth.

Refresh rate increase

But there is one thing. When I turned on these two phones for the first time, the two phones’ default refresh rate was 60Hz instead of the main 120Hz, which requires the user to turn it on manually. Since the Redmi K40 dual flagship has prepared such a high-quality screen, why not default to 120Hz in one step so that users can directly experience the smoothest state of this screen? If you are worried about power consumption, you can prompt boot settings and let consumers choose the refresh rate.

In addition to the above-mentioned screen material, brightness, refresh rate, sampling rate, and other parameters, these two phones’ parameter has also been greatly improved: colour accuracy. In the colour adjustment, the screen JNCD≈0.36, ΔE≈0.35, this kind of colour calibration-level has reached the current first-class level, which can restore and display its colour. Moreover, this time the K40 Pro screen has obtained DisplayMate A+ certification, which is evident in the high screen quality.

Also, Redmi K40 and K40 Pro provide many colour modes and custom adjustment space in the settings-display-colour style. Based on my personal feelings, switching to another colour mode is recommended when you get it or directly select P3 or sRGB in the advanced mode. The colour display is much more accurate. The colour performance of the default adaptive mode is a bit too gorgeous. At first glance, it is indeed very dazzling and gorgeous, but it seems tired after watching it for a long time. It is recommended that the official follow-up adjustment of the colour performance of the adaptive mode.

True Tone true colour display

It is worth noting that Redmi K40 and K40 Pro have added a special feature-True Tone true colour display. The mobile phone has a built-in dedicated ambient light sensor, which can detect ambient light colour information through multiple internal light channels and then adjust the screen colour temperature according to different ambient light to make the display colour temperature more in line with the ambient colour temperature. For example, in the night environment, the mobile phone screen’s colour temperature will be significantly warmer, reduce the brightness, and maintain a more comfortable screen look and feel. When you go to another light environment, the screen colour temperature will change accordingly.

However, this screen’s “cold” and “warm” colour temperature is temporary, aiming to adjust a colour temperature suitable for the current environment to make it more comfortable for the naked eye. Also, this function will not cause damage to the screen, and the power consumption caused by this function is almost negligible.

Although there are some minor flaws, these problems are software problems, which can be improved and corrected later, and do not affect the screens’ high quality on the Redmi K40 and K40 Pro. Moreover, the K40 series can use the same high-quality screens on mobile phones of the same series and different locations at this price, allowing more consumers to use high-quality and high-specification screens, which shows the sincerity of the K40 series this time.


Redmi K40 and K40 Pro all adopt a middle hole design. The screen opening is located at the centre of the screen’s top, but the opening diameter is only 2.76mm. The opening is perfect for comparison. The length of a sesame seed is about 2mm to ensure the look and feel. Under the premise of being integrated with the fuselage, the impact of punching on the overall screen look and feel is minimized.

Punch Hole screen

In the early warm-up of the K40 series, there was feedback that this phone’s frame was relatively wide. But this is not the case with the real machine. The Redmi K40 and K40 Pro have basically the same frame width, with narrow left and right frames and similar widths on the four sides, to maintain a more balanced look and feel visual. Also, as far as the bottom frame is concerned, it is actually not wide, and it appears wide only because of the visual difference caused by the colour of the middle frame and the colour of the frame. If you are concerned, you can go to an offline physical store to experience it for yourself.

The highlight of the appearance this time, in addition to the ultra-small openings, there is also this colour matching. Redmi K40 Pro comes in three colours: Ink Feather, Sunny Snow, and Fantasy Land. The historic Damascus steel knife inspires the ink feather design. After 11 processes and hundreds of attempts, this phone finally combines the characteristics of this steel knife. The lines are re-engraved on the phone. The special texture undulates with the flow of light, and this texture also incorporates gradual design elements. The texture colour changes from dark to light, gradually extending from the edge of the fuselage to the inside. With the black back cover, it is not obtrusive and high—the degree of recognition.


Redmi K40 comes in three colours: Bright Black, Sunny Snow, and Fantasy Land. Among them, Sunny Snow and Fantasy Land are the colours shared by the two phones. The former uses AG glass technology to highlight white cleanness and purity, while the latter is mainly blue. The multi-layer film can show dynamic light, shadow and colour effects.

Top speaker

In some details, the camera part and brand logo arrangement of Redmi K40 and K40 Pro adopts a design language similar to Xiaomi 11. Also, both phones are equipped with Dolby stereo symmetrical dual speakers and X-axis linear motors. It is worth noting that the Redmi K40 and K40 Pro’s weight and thickness are both 196g and 7.8mm. The built-in 4520mAh battery under the premise of limited space in the fuselage achieves a balance of lightness and battery life. This is worthy of praise.

Side fingerprint unlock

Another point is that side fingerprints unlock both phones, and the fingerprint power button is two-in-one. Still, instead of using the traditional groove design, the fingerprint power button’s appearance is the same as that of the normal power button keeping the body of the phone. Oneness. Functionally, in the settings-more settings, you can add more shortcuts to the fingerprint power button, for example, tap the fingerprint button twice to open the payment code, scan, camera, voice assistant, etc.; after receiving OTA updates in the future, It can also quickly call up the health treasure and expand the application space of fingerprints. Thee Redmi K40 and K40 Pro appearance is more recognizable than the previous generation, especially the ultra-small holes, ink feather colour matching, and the camera design, which are enough to make people recognize that this is a mobile phone belonging to the K40 series.


Redmi K40 vs Redmi K40 Pro

The previously released K30 and K30 Pro use the Snapdragon 765G and Snapdragon 865, respectively. This time, the K40 dual flagships all use the Snapdragon 8 series chips positioned as flagships. Redmi K40 is equipped with Qualcomm Snapdragon 870, while K40 Pro is equipped with Qualcomm Snapdragon 888 with an advanced 5nm process. The performance is significantly improved compared with the previous generation. Moreover, the K40 series is also Redmi’s first series of products equipped with these two chips.

Redmi K40 vs Redmi K40 Pro

In the Antutu running points, the Redmi K40 Pro equipped with the Snapdragon 888 has a running score of 727,853 points, and the Redmi K40 using the Snapdragon 870 has a running score of 631,320. The running scores of both have reached the current mainstream flagship level, but it is clear that the 5nm process technology and Cortex-X1 super core Snapdragon 888 have a higher performance level.

Redmi K40 vs Redmi K40 Pro

At the CPU level, the Redmi K40 Pro has a single-core score of 5059 points and a multi-core score of 14,919 points, while the K40’s single-core and multi-core scores are 4587 points and 13,362 points, respectively. The CPU part directly determines the performance of a chip. It can be seen that the performance of the two mobile phones has reached the flagship level.

In the GPU part that determines the graphics processing capabilities, the Redmi K40 Pro scored 7477 points in the 3D Mark OpenGL ES 3.1 test, and the K40 scored 6298 points. K40 Pro relies on the Adreno 660 integrated by Snapdragon 888 to obtain excellent graphics processing capabilities, which means that K40 Pro can obtain higher game picture quality and more stable game frames in games, especially in high-frame games. In.

It is worth noting that both Redmi K40 Pro and K40 mobile phones support “90 Nephew of Glory”, but relatively, this also puts forward higher requirements on mobile phone performance. It can be seen from the above two frame number graphs that the average frame number of K40 is 90.5 frames, and the overall operation is smooth. Still, there is a certain frame number fluctuation. In contrast, the average frame number of K40 Pro is 92.5 frames, the running effect is very smooth, and the frame number curve Stable and relying on Snapdragon 888, with better game picture quality.

In “Peace Elite”, the performance of the two is basically the same. Under the highest image quality that can be turned on, the frame number curve is stable, and the operation runs smoothly. After the entire game experience, there is basically no frame drop phenomenon.

However, in the “Original God”, which has a very high configuration of mobile phones, the performance gap between the two will be more obvious. Under the premise of the highest image quality and 60 frames, the average frame number of the K40 is only 31.1 frames, and there is an obvious phenomenon of symptom-dropping. Still, after reducing the image quality and frame number requirements, the smoothness has been restored. On the premise of the highest image quality and 60 frames, the K40 Pro equipped with Snapdragon 888 has an average frame rate of 59.8 frames. The game frame rate is more stable and smooth, there is no obvious lag, but the picture is clearer and brighter.

Also, this time, the Redmi K40 series debuts 360Hz three-finger touch and super-resolution touch, which can greatly enhance the sense of the game’s operation, and the screen in the game is more user-friendly. Users can customize the hand control and sensitivity in the game acceleration-advanced settings and customize the touch sensor according to their own operating habits.

X-axis linear motor

Simultaneously, to further enhance the immersion of the game, the K40 series has been specially optimized for the X-axis linear motor so that the motor vibration is integrated into each use scene, and the interaction is more three-dimensional. Moreover, the vibration has been customized for “Peace Elite”, and every shot, driving, and other operations are more realistic.

However, for the improvement of the game and the hardware itself, a stable network connection is also required. Redmi K40 Pro supports WiFi 6 enhanced version and dual 5G dual card dual standby. While bringing faster network speed, it can also effectively reduce game delay. With a Multi-Link 5.0 multi-network parallel connection, WiFi instantaneously cuts the 5G network to ensure gaming Always online.

In addition to the chip upgrade, Redmi K40 Pro is equipped with a 3200MHz full-blood version of LPDDR5 memory, and the data transfer rate can reach 6400Mbps. The full blood version of LPDDR5 memory and UFS 3.1 flash memory are paired with Snapdragon 888, and the three work together to keep the phone running smoothly. Redmi K40 uses 2750MHz LPDDR5 memory, with a data transfer rate of up to 5500Mbps, and it can also achieve high processing efficiency and speed with the Snapdragon 870.

The chip part is one of the upgrade points of the Redmi K40 series. The entire series is equipped with flagship Snapdragon 8 series chips, which makes the performance of the K40 series significantly improved compared with the previous generation, making it more obvious when facing products at the same price. Advantage.


In the camera section, Redmi K40 and K40 Pro are both rear-mounted three-camera combinations. The former is equipped with a 48-megapixel main camera, an 8-megapixel ultra-wide-angle camera and a 5 million telephoto macro. The K40 Pro is equipped with a 64-megapixel main camera and 8 million pixels. Ultra-wide-angle camera and 5 million telephoto macro. In addition to hardware, these two phones integrate many photo and video post-production functions in the photo editing function, including one-click beautification, filters, and other functions such as magic sky change, which greatly improves the playability of taking pictures.

Since the two’s editing functions are the same, this part takes Redmi K40 Pro as an example. This phone provides users with wealthy post-editing functions in the album-editing, especially the “one-click beautification” function, which is also my personal editing function, which can adjust the saturation, contrast, brightness, etc., of the original image Parameters, and then get a more suitable photo for sharing.

Taking this group of proofs as an example, it can be clearly seen that the overall look and feel of the photo after processing has been improved, and the colour of the picture has become more colourful, attracting attention. Basically, the photos processed with this function can better look and feel than the original image.

Night Mode

Redmi also integrates popular, classic, portrait, movie, gourmet and other different filters in the filter function, and the colour of the filter can be adjusted. In addition, the classic magic sky changing function in MIUI is also inherited.

These two phones provide users with a lot of post-production space in the post-editing function, greatly improving the playability of the camera function, and can better adjust the photo style according to their own wishes. It is a good thing to have abundant post-production functions, so what is the quality of the camera itself?

In the daytime environment, the imaging style of the Redmi K40 Pro is more inclined to restore the picture seen by the naked eye as much as possible. From the proofs, this phone’s image is clear; relying on the processing speed of Snapdragon 888, the photo imaging is fast. Also, the brightness and colour of the photos are balanced, which can meet the aesthetics of most people.

Green Mode

Compared with the daytime, the K40 series performs more clearly in the night scene. K40 Pro can still get good picture quality at night with complicated light, and the imaging speed is still fast. It is worth noting that the night scene photos of this phone have a high degree of purity and the noise is well controlled. However, the strong light in the night scene, such as the building’s indoor lighting, is prone to a certain degree of overexposure. Still, fortunately, it will not cause obvious negative effects on the picture. The special night scene mode can well improve the night scene imaging level of the Redmi K40 Pro.

While controlling the exposure, it improves the picture’s clarity by enhancing the sharpness of the photo while retaining the atmosphere of the night scene itself. For example, in the above two sets of proofs, the night scene mode’s exposure and clarity are significantly improved compared to the original image. Also, when shooting night scenes, it is still recommended to turn on the built-in black gold, green orange, and other phone filters to obtain night scene effects with different styles.

Macro mode

The existence of the telephoto macro provides another perspective for the user to take pictures. When the user shoots an object at an ultra-close distance, the picture is clear, and it also has a certain blur effect to strengthen the subject.

The imaging style of the Redmi K40 is basically the same as that of the Pro version. It also has a good imaging effect in scenes such as daytime. However, because it uses a 48-megapixel main camera, it will be slightly inferior to the K40 Pro in picture resolution. Look at the proofs.


Redmi K40 and K40 Pro have many things in common in configuration, such as battery capacity. These two phones have a built-in 4520mAh battery while maintaining a thin and light body, taking into account consumers’ needs for long battery life and a thin and light body. For comparison, the K30 5G, a perforated structure before, is equipped with a 4500mAh battery, weighs 208g, and has a thickness of 8.79mm. It can be seen that while the K40 series achieves configuration upgrades, the internal structure of the internal fuselage has also improved.

In terms of charging power, both phones support up to 33W wired fast charging. It takes 55 minutes to fully charge Redmi K40 from 0%, 36% in 15 minutes, and 67% in 30 minutes, while K40 Pro takes 57 minutes from 0% to fully charged, and 35% in 15 minutes. It can be charged to 63% in 30 minutes. Although there is a gap of 2 minutes, the gap is not large and will not hurt normal use.

It is worth noting that both K40 and K40 Pro phones are equipped with a 33W charging head and data cable as standard packaging to meet consumer demand for essential accessories.

Read Also: Redmi MAX 86 Smart TV Review: Big Cinema Display at Your Home


In terms of screen, chip, battery life, user experience, and other aspects, the Redmi K40 series has been greatly upgraded, coupled with its highly competitive price. This generation of products has a more obvious cost-effective advantage. At the same time, under the guidance concept of “all series upgrade cups”, K40 has enough strength to take over last year’s K30 Pro, while K40 Pro and subsequent models can let go of their hands and feet to continue to upgrade and even explore higher price segments, and then Promote the upgrade of the Redmi brand. But at the same time, Redmi will not give up its cost-effective advantage, which is evident from this K40.

Therefore, for the K40 series of the “full series of rising cups”, I think it can be regarded as an attempt by Redmi to develop upwards. Perhaps in the future, we can see that Redmi will have more “lifting cups” products and continue to consolidate and improve itself in the industry’s market and position. There is no doubt that the K40 series can and must make a good start for Redmi’s new 10-year road.


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