Xiaomi 15 Ultra Review: Strong but Not Perfect
Our full Xiaomi 15 Ultra review after two weeks of testing: measured performance, battery figures, and whether it is worth £1299.
Aisha Bello
The short version
The Xiaomi 15 Ultra is Xiaomi's 2025 entry in a crowded smartphones market, and at £1299 it is competing against some of the strongest hardware we have tested. After a fortnight of daily use, the headline is straightforward: it delivers a one-inch main sensor with genuinely optical depth falloff.
The one-line answer: Buy it for a one-inch main sensor with genuinely optical depth falloff. Think twice if this would bother you daily: heavy.
Design and build
There is nothing experimental here, which is mostly to the Xiaomi 15 Ultra's credit. The detail worth calling out is that night mode is rarely needed at all thanks to the sensor size. Against the rest of the smartphones category it feels considered rather than novel.
What it can do
Our testing runs the same suite on every device so figures stay comparable across years. The figure worth quoting is Screen-on time: 7h 05m. That places it comfortably above average for its price bracket.
| Specification | Xiaomi 15 Ultra |
|---|---|
| Display | 6.73in LTPO AMOLED, 120Hz |
| Chip | Snapdragon 8 Elite |
| RAM | 16GB |
| Battery | 5410mAh |
| Charging | 90W wired |
| Weight | 226g |
| Screen-on time | 7h 05m |
How we tested
Every figure quoted above comes from the same protocol, run on every unit in this category. This one spent fourteen days as the reviewer’s only phone, SIM included. Screen at a metered 200 nits, adaptive refresh left on, the same twelve apps installed on every handset, and a fixed 5G network in the same building.
| What we measure | How |
|---|---|
| Screen-on time | A scripted day — four hours of mixed browsing, an hour of video, thirty minutes of camera, the rest idle — repeated three times and averaged. |
| Sustained performance | Twenty minutes of continuous load, reporting the figure at the end rather than the peak in the first ninety seconds. |
| Charging | From 2% to 100% with the fastest charger the manufacturer sells, at 22°C ambient, timed to the minute. |
| Camera | The same eighteen scenes on every phone — backlit portrait, indoor low light, moving subject — shot in the default mode with no editing. |
| Thermals | Surface temperature at the hottest point after the sustained run, measured with a contact probe. |
We deliberately do not report synthetic benchmark totals quoted in isolation, and any figure supplied by the manufacturer.
The honest caveat: Battery results are specific to our routine. A heavy camera user will see materially less screen-on time than these numbers suggest.
What it does well
- A one-inch main sensor with genuinely optical depth falloff
- An optional grip with a physical shutter
- Very fast charging
Taken together, those strengths make it a natural fit for photographers who want the closest thing to a compact camera in a phone.
Where it falls short
- Heavy
- Noticeable preinstalled software bloat
- A shorter update commitment than Google or Samsung
None of these are dealbreakers on their own. Whether they matter depends entirely on how you intend to use it, which is why the section below matters more than the score.
How it compares
The closest alternatives on price are Galaxy S25 Ultra and iPhone 16 Pro. All three have been through the same tests, so the figures below are directly comparable rather than collected from different reviews.
| Model | Price | Our score | Standout | Weak point |
|---|---|---|---|---|
| Xiaomi 15 Ultra (this review) | £1299 | 4 / 5 | A one-inch main sensor with genuinely optical depth falloff | Heavy |
| Galaxy S25 Ultra | £1249 | 4 / 5 | The best long telephoto on any phone | Heavy at 232g |
| iPhone 16 Pro | £1099 | 4 / 5 | The best sustained performance of any phone | Iterative to a fault |
Nothing at this price scored higher in our testing, which is the strongest argument for the Xiaomi 15 Ultra.
Is it worth the money?
At £1299 the Xiaomi 15 Ultra asks £374 more than the category average of £925, against an average score of 4.1 out of 5 across the smartphones we have tested. Its own 4 works out at roughly £325 per point. Paying above average for a below-average score only makes sense if photographers who want the closest thing to a compact camera in a phone describes you precisely.
If the budget is the binding constraint, the Galaxy A56 at £399 is the floor we would still recommend — below that the compromises stop being ones you can live with.
Living with it
Two weeks in, the figure that stopped mattering was display — 6.73in LTPO AMOLED, 120Hz is more than adequate and you forget about it by the third day. What kept surfacing instead was that heavy, which is easy to shrug off in a spec comparison and harder to ignore at 6pm on a Friday. On the other side, night mode is rarely needed at all thanks to the sensor size turns out to be the sort of detail you only appreciate after living with the alternative.
Who it suits
Buy the Xiaomi 15 Ultra if you are photographers who want the closest thing to a compact camera in a phone. Skip it if this is something you would notice every day: heavy.
Buy it if:
- Photographers who want the closest thing to a compact camera in a phone
- You want a one-inch main sensor with genuinely optical depth falloff
- You value an optional grip with a physical shutter
Skip it if:
- You need heavy to be a solved problem
- The Galaxy S25 Ultra at £1249 already covers what you need
- You upgraded within the last two years — the gap is not worth the outlay
Verdict
Buy it for a one-inch main sensor with genuinely optical depth falloff. Think twice if this would bother you daily: heavy.
Score: 4 / 5 · £1299 at the time of writing.
Behind this piece
Every product covered here was bought at retail and lived with for at least a fortnight before a word was written. Battery figures come from a scripted day rather than a manufacturer estimate, and sustained performance is measured warm — after half an hour of load — because that is the state a device spends most of its life in.
Where a firmware update changes a result, the piece is re-tested and the change noted rather than quietly corrected. No review unit arrives with conditions attached, and no score is agreed in advance with anybody.
Where to go next
If you are weighing this against the rest of the smartphones we have covered, the category archive lists every review in date order. The closest comparisons we have published are Xiaomi 15 Ultra vs Galaxy A56: Is the Xiaomi 15 Ultra Worth £900 More? and Xiaomi 15 Ultra vs Pixel 9a: Is the Xiaomi 15 Ultra Worth £800 More?.
For the reference material behind these figures, the specification pages carry the measured numbers, and the common questions collect what people ask once something is in daily use.
