Samsung Galaxy S21 Ultra vs Samsung Galaxy S25
Our Verdict: The Galaxy S21 Ultra and the Galaxy S25 are four years apart, which is enough for a real difference. The S21 Ultra 5G has a considerably higher-resolution main camera, 108MP against the S25's 50MP, plus a 40MP selfie camera against 12MP, and there's more battery in the S21 Ultra 5G, 5000mAh to 4000mAh, which should mean longer between charges in day-to-day use. The S21 Ultra 5G has the stronger screen, bigger at 6.8" against 6.2" and sharper at 516 PPI, and the S25 is the lighter phone at 162g against 228g. If you're on the S21 Ultra 5G, the S25 is a real step up, but only worth it if the changes above matter to you.
Buying outright, the S21 Ultra 5G starts at £235 SIM-free.
10 reviews 4.1
11 reviews
Prices updated 26 July 2026
Samsung Galaxy S21 Ultra
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Samsung Galaxy S25
|
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|---|---|---|
| Expert Rating | 4.4 10 reviews |
4.1 11 reviews |
| Screen | 6.8" | 6.2" |
| Display | Dynamic AMOLED 2X capacitive touchscreen | Dynamic LTPO AMOLED 2X |
| Resolution | 1440 x 3200 | 1080 x 2340 |
| Pixels Per Inch | 516 | 416 |
| Rear Camera | 108 Megapixels | 50 Megapixels |
| Front Camera | 40 Megapixels | 12 Megapixels |
| Chipset | Exynos 2100 | Qualcomm SM8750-AB Snapdragon 8 Elite (3 nm) |
| Battery | 5,000 mAh | 4,000 mAh |
| Storage | 128GB, 256GB, 512GB | 128GB, 256GB, 512GB |
| OS | Android 11 | Android 15 |
| SIM Type | Nano SIM | nano-SIM and e-SIM |
| Connectivity | Up to 5G | Up to 5G |
| Wi-Fi | 802.11 a/b/g/n/ac/6 | 802.11 a/b/g/n/ac/6e |
| Bluetooth | 5.1 with A2DP, LE | 5.4, A2DP, LE |
| Dimensions | 165.1 x 75.6 x 8.9 mm | 146.9 x 70.4 x 7.2 mm |
| Weight | 228 grams | 162 grams |
| Water Resistance | IP68 - Dust and water resistant over 1.5 meter and 30 minutes | IP68 - Dust and water resistant over 1.5 meter and 30 minutes |
| Contracts | - |
£22.00/mo
£20.00 upfront |
| SIM-free | £234.99 | £439.99 |
| Prices updated 26 July 2026 | ||
| Deals | Deals | |
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Frequently Asked Questions
Which has the better screen, the Samsung Galaxy S21 Ultra or Samsung Galaxy S25?
The Samsung Galaxy S21 Ultra has the bigger screen at 6.8" compared to the Samsung Galaxy S25's 6.2", the Samsung Galaxy S21 Ultra has the sharper display at 516 pixels per inch versus 416, and the Samsung Galaxy S21 Ultra uses a Dynamic AMOLED 2X capacitive touchscreen panel while the Samsung Galaxy S25 has a Dynamic LTPO AMOLED 2X.
Which has the better camera, the Samsung Galaxy S21 Ultra or Samsung Galaxy S25?
The Samsung Galaxy S21 Ultra features a 108 Megapixels rear camera, while the Samsung Galaxy S25 has a 50 Megapixels rear camera. Both devices also have front-facing cameras for selfies and video calls.
Which is cheaper to buy SIM-free, the Samsung Galaxy S21 Ultra or Samsung Galaxy S25?
The Samsung Galaxy S21 Ultra is cheaper SIM-free, starting from £234.99.
What storage options are available for the Samsung Galaxy S21 Ultra and Samsung Galaxy S25?
The Samsung Galaxy S21 Ultra is available in 128GB, 256GB, 512GB, while the Samsung Galaxy S25 comes in 128GB, 256GB, 512GB.
What processors do the Samsung Galaxy S21 Ultra and Samsung Galaxy S25 use?
The Samsung Galaxy S21 Ultra is powered by the Exynos 2100, while the Samsung Galaxy S25 uses the Qualcomm SM8750-AB Snapdragon 8 Elite (3 nm).
Which is easier to carry and hold, the Samsung Galaxy S21 Ultra or Samsung Galaxy S25?
The Samsung Galaxy S25 is the more portable of the two: it's 66g lighter at 162 grams, it's also the more compact phone at 146.9 x 70.4 x 7.2 mm, and is slimmer at 7.2mm thick.
Which is more water resistant, the Samsung Galaxy S21 Ultra or Samsung Galaxy S25?
Both phones share the same water resistance rating of IP68 - Dust and water resistant over 1.5 meter and 30 minutes.
What operating system do the Samsung Galaxy S21 Ultra and Samsung Galaxy S25 run?
The Samsung Galaxy S21 Ultra runs Android 11 and the Samsung Galaxy S25 runs Android 15. This is one of the biggest factors when choosing between the two, as each ecosystem has its own apps, services and features.