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Phone zoom and print size
A straight crop of z times keeps 1/z² of the pixels, so at the 100 pixels per inch rule a 12 MP photo can be cropped about 2.2x for a 12 x 18 in print but only 1.0x for 30 x 40 in, while a 200 MP photo can be cropped 4.5x for 24 x 36 in.
Pixels left after a crop, against 12 x 18 and 24 x 36 in. A bar must pass the dashed line to meet the rule.
How far can you crop for each size?
The factor is the largest crop that still has 100 pixels per inch on both sides of the print: min(width / (100 x long side), height / (100 x short side)) for a 4:3 frame. 1.0x means no crop at all; a factor below 1.0 means the full frame is already short.
| Listed size (in) | MP needed | 12 MP | 24 MP | 48 MP | 50 MP | 108 MP | 200 MP |
|---|---|---|---|---|---|---|---|
| 8 x 10 | 0.8 | 3.8x | 5.3x | 7.5x | 7.7x | 11.2x | 15.3x |
| 12 x 18 | 2.2 | 2.2x | 3.1x | 4.4x | 4.5x | 6.7x | 9.1x |
| 16 x 24 | 3.8 | 1.7x | 2.4x | 3.3x | 3.4x | 5.0x | 6.8x |
| 20 x 30 | 6.0 | 1.3x | 1.9x | 2.7x | 2.7x | 4.0x | 5.4x |
| 24 x 36 | 8.6 | 1.1x | 1.6x | 2.2x | 2.3x | 3.3x | 4.5x |
| 30 x 40 | 12.0 | 1.0x | 1.4x | 2.0x | 2.0x | 3.0x | 4.1x |
| 36 x 48 | 17.3 | below 100 ppi | 1.2x | 1.7x | 1.7x | 2.5x | 3.4x |
| 48 x 60 | 28.8 | below 100 ppi | below 100 ppi | 1.2x | 1.3x | 1.9x | 2.6x |
Example: a 200 MP frame is about 16,329 x 12,246 pixels; a 24 x 36 in print needs 2,400 x 3,600. 16,329 / 3,600 = 4.5 and 12,246 / 2,400 = 5.1, so the limit is 4.5x, set by the long side.
What a zoom setting leaves
Each cell is the megapixels left after a straight crop, followed by the largest listed size that crop reaches.
| Crop | 12 MP | 24 MP | 48 MP | 50 MP | 108 MP | 200 MP |
|---|---|---|---|---|---|---|
| 1x | 12.0 MP, 30 x 40 | 24.0 MP, 36 x 48 | 48.0 MP, 48 x 60 | 50.0 MP, 48 x 60 | 108.0 MP, 48 x 60 | 200.0 MP, 48 x 60 |
| 2x | 3.0 MP, 12 x 18 | 6.0 MP, 20 x 28 | 12.0 MP, 30 x 40 | 12.5 MP, 30 x 40 | 27.0 MP, 40 x 60 | 50.0 MP, 48 x 60 |
| 3x | 1.3 MP, 10 x 12 | 2.7 MP, 12 x 18 | 5.3 MP, 20 x 24 | 5.6 MP, 20 x 24 | 12.0 MP, 30 x 40 | 22.2 MP, 36 x 48 |
| 4x | 0.8 MP, 6 x 10 | 1.5 MP, 10 x 12 | 3.0 MP, 12 x 18 | 3.1 MP, 12 x 18 | 6.8 MP, 20 x 30 | 12.5 MP, 30 x 40 |
| 5x | 0.5 MP, 6 x 8 | 1.0 MP, 8 x 10 | 1.9 MP, 12 x 12 | 2.0 MP, 12 x 12 | 4.3 MP, 18 x 24 | 8.0 MP, 20 x 30 |
| 10x | 0.1 MP, none | 0.2 MP, none | 0.5 MP, 6 x 8 | 0.5 MP, 6 x 8 | 1.1 MP, 8.3 x 11.7 | 2.0 MP, 12 x 12 |
What the phone makers state
Apple lists digital zoom up to 10x on the iPhone 16 and 17 pages and a '12MP 2x Telephoto' enabled by the 48MP main camera, which matches 48 / 4 = 12. Samsung's S25 Ultra page says zoom past 10x may express some image deterioration. Xiaomi's Redmi Note 13 5G page lists a '3X In-Sensor Zoom' on its 108MP camera, which by the same arithmetic leaves 108 / 9 = 12 MP. Where a phone has a separate telephoto sensor, its photos are not a crop of the wide camera, so the table applies only to the digital part of a zoom.
The table counts sensor pixels only. A zoomed photo may be saved at a larger size than the crop holds; the pixel count of the file then says nothing about detail. Sizes use a 4:3 frame from megapixels, rounded down.
Sources
- Apple India: iPhone 16 tech specs (manufacturer page), fetched 2026-11-13
- Apple India: iPhone 17 tech specs (manufacturer page), fetched 2026-11-13
- Samsung India: Galaxy S25 Ultra (manufacturer page), fetched 2026-11-13
- Xiaomi India: Redmi Note 13 5G specs (manufacturer page), fetched 2026-11-13