Xiaomi 15 Ultra review

6.73-inch OLED display is all sorts of nice

The Xiaomi 15 Ultra's display appears unchanged in its specs compared to the previous generation. A 6.73-inch QHD OLED panel, it supports adaptive refresh rate in the 1-120Hz range, features both 1920Hz PWM and DC dimming, and can show up to 68 billion colors. HDR10+ and Dolby Vision are both on the menu as well.

What has changed, looking at our test results, is the display's maximum brightness - we measured 1,599nits in auto mode, some 300nits higher than on the 14 Ultra. In manual mode, the number was 841nits with Sunlight mode enabled (629nits otherwise). We'd call the phone's results average - it's just that we'd have to try and explain that's not a bad thing, given the level where 'average' is now.

Refresh rate

Refresh rate is handled in more or less the usual Xiaomi way - with a 'Default' (full auto) mode and two Custom modes (120Hz and 60Hz ceilings). Regardless of mode, the phone will be doing its adaptive magic, with the only real control you have over it being the 60Hz cap in one of the custom modes - it will readily dial down to 1Hz when idle and it will shoot all the way up to 120Hz in both Custom 120Hz and Default modes. It will also pick any refresh rate its algorithms choose to be the right one for the moment - no fixed steps.

Dedicated fixed refresh rate modes will be engaged for the corresponding video frame rates - 24, 30, 48, and 60fps are covered.

We had a somewhat unreliable experience with games, with most of our usual titles actually maintaining a 60fps cap. The frame rate and the refresh rate would go above that once we pulled up the gaming utility that reported the fps, but in its own history for the preceding moments the frame rate would have been up to 60fps.

Streaming and HDR

The 15 Ultra supports HDR10+ and Dolby Vision. YouTube happily served HDR content, as did Netflix, also reporting it supported both standards. High-res video playback of DRM-protected content is covered too, thanks to the Widevine L1 compliance.

The Android Ultra HDR standard for photos is also supported and it's one of the more straightforward implementations, where it just works where it should - Google Photos, Chrome, the in-house gallery.

Xiaomi 15 Ultra battery life

The Xiaomi 15 Ultra, in its global form, is powered by a 5,410mAh battery of the silicon carbon type. It's a welcome increase over the 5,000mAh capacity of the previous model, though a lot of this year's... important models pack even more mAhs. Now, the 15 Ultra for China does come with a 6,000mAh power pack, itself an increase over the Chinese 14 Ultra's 5,300mAh capacity, but the world gets different numbers.

In our testing, the 15 Ultra showed a marked improvement over the previous generation's results across the board. We clocked 13:18h of web browsing, which is more or less the norm for this year's flagship models, 19:25h of looping videos (at the higher end of the charts), and 10:41h in the gaming test (also longer than most). The 40:51h of voice call endurance is also way above average. Ultimately, the overall Active Use Score of the Xiaomi 15 Ultra is a class-leading 16:13h.

Our new Active Use Score is an estimate of how long the battery will last if you use the device with a mix of all four test activities. You can adjust the calculation based on your usage pattern using the sliders below. You can read about our current battery life testing procedure here. For a comprehensive list of all tested devices so far, head this way.

Charging speed

The 15 Ultra ships without a charger, but is rated for up to 90W of power - not just with Xiaomi adapters, but regular USB Power Delivery ones, provided they can get the numbers right. Still, we tested with a Xiaomi 90W adapter after all, the one we had from the 14 Ultra - it supports several flavors of PPS, including 3.6-20V@4.5A, so maybe that's what you should be looking for when picking up a third-party charger. We got the highest peak power of around 76W in the early stages of the process, with the usual ramp down as the percentages grew.

So with that 90W adapter we clocked a full charge from flat at around 51 minutes, with the battery indicator showing 72% at the half-hour mark. It's notably slower than last year's model, but such are the trends this generation. It's still quicker than the S25 Ultra, Pixel 9 Pro XL and the iPhone 16 Pro Max, for what little that's worth. The likes of the vivo X200 Pro and the Find X8 Pro are about on par with the Xiaomi, while the OnePlus 13 is faster to charge and so too is the Magic7 Pro (albeit in Euro trim with the smaller 5,270mAh battery).

Now, we're being told that this particular adapter is a little hard to find, but even without it, there's every chance you may still be able to get this highest possible charging speed.

We tried with a handful of other Xiaomi adapters we had in the office. For starters, the 120W unit got us essentially the same numbers as the 90W one. We also tried a 67W Xiaomi adapter and we actually got ever so slightly better results for speed than the 90W option - 49 minutes to full, 77% at the half-hour mark, 58W highest power. Using the 45W Xiaomi adapter, the results weren't quite as good, but decent nonetheless - 65 minutes, 62%, 29W.

It gets more complicated with aftermarket chargers. We tried a 100W one and a 65W one, both from reputable brands, and the peak power we got with them was 46W and 39W respectively, for what that's worth. We were looking at 59% at the 30-minute checkpoint and 90 minutes to full - essentially the same results with either. We'd say the half-hour results are alright, but the full charge time is a bit of a letdown.

The thing is, the phone maxes out its charging power and speed when the adapter on the other end of the cable can do PPS at 18-19V, which requires a PPS profile that goes up to 20V. A lot of the aftermarket adapters don't have such a PPS profile - the two that we tried, for example, have PPS up to 16V or 11V, in which case the phone charges at around 9V, which apparently limits its speed.

The 15 Ultra also supports wireless charging, and Xiaomi quotes 80W as the maximum power, though you will need a proprietary charger for that. There's no mention of Qi 2 support in the press materials.

A handful of measures to prolong the 15 Ultra's battery health are available in settings including limiting the fast charging by switching from Top speed to Standard. You can also enable Smart charging which will charge the phone up to 80% and then top off just before you typically use it (based on learning your usage patterns). Or just set a hard limit on things at 80% in all situations by enabling the Battery protection toggle.

Speaker test

The 15 Ultra features a stereo speaker system with a down-firing unit on the bottom, and a front-firing speaker/earpiece combo - there's no longer a grille on the top plate, so no sound spillage when you're on a voice call (if that's even ever a consideration for anyone).

Bottom speaker • Top speaker/Earpiece

We got a 'Very Good' rating for loudness out of the 15 Ultra, like essentially every other high-end phone in recent times, though the Xiaomi does admittedly have a small advantage in the numerical result. The phone also puts out excellent sound quality, superior to that out of the Find X8 Pro and vivo X200 Pro, and possibly the Galaxy S25 Ultra. The iPhone 16 Pro Max just may be a little bit better still.

Use the Playback controls to listen to the phone sample recordings (best use headphones). We measure the average loudness of the speakers in LUFS. A lower absolute value means a louder sound. A look at the frequency response chart will tell you how far off the ideal "0db" flat line is the reproduction of the bass, treble, and mid frequencies. You can add more phones to compare how they differ. The scores and ratings are not comparable with our older loudspeaker test. Learn more about how we test here.