DocVerify Pro › Scan at 300 DPI with a phone
“Scan at 300 DPI” — from a phone that has no DPI setting
Almost every agency asks for 300 DPI. No phone camera offers that setting, which makes the instruction look impossible. It is not: DPI is not a camera setting at all, it is the result of a division, and once you see the arithmetic you can tell instantly whether a photo qualifies.
The short answer. DPI = pixels ÷ inches. A US Letter page is 8.5×11 inches, so 300 DPI means about 2550 × 3300 pixels of page. Any modern phone exceeds that easily — as long as the page fills the frame.
What DPI really is
Dots per inch is a ratio between a number of pixels and a physical size. A file does not have a DPI until you say how big it is meant to be on paper. The same 2550×3300 image is 300 DPI on a Letter page and 150 DPI on a poster twice the size. That is why your camera has no DPI setting: it does not know what size you intend to print.
The arithmetic, for the usual page sizes
| Page | Inches | Pixels needed for 300 DPI |
|---|---|---|
| US Letter | 8.5 × 11 | 2550 × 3300 |
| A4 | 8.27 × 11.69 | 2480 × 3508 |
| US Legal | 8.5 × 14 | 2550 × 4200 |
| ID card (CR80) | 3.37 × 2.13 | 1011 × 638 |
Why your 12-megapixel photo can still fail
A 12 MP phone photo is around 4032×3024 pixels — comfortably more than 300 DPI needs. It fails when most of those pixels are not the document. Photograph a page from far away, with desk and hands around it, and the page itself might occupy only 1400 pixels across. Cropping afterwards cannot invent detail: those are the only pixels that ever existed.
So the rule that matters is not megapixels. It is: fill the frame with the page.
How to actually get there
- Put the document on a flat surface with even light — near a window, not under a ceiling lamp that casts your own shadow.
- Hold the phone parallel to the page, directly above the centre. Shooting at an angle loses resolution on the far edge and distorts the shape.
- Move close enough that the page nearly touches all four edges of the frame. A small margin is fine; a desk in shot is not.
- Tap the screen to focus on the text, and hold still. Blur destroys effective resolution no matter how many pixels the sensor recorded.
- Do not use flash. It creates a bright blown-out patch that usually lands on exactly the field a reviewer needs.
Is more than 300 DPI better?
No, and it costs you. 600 DPI quadruples the file size for detail a reviewer will never look at, and it is the fastest way to run into an upload size limit. 300 DPI is the standard because it is where printed text stops improving to the human eye. Go above it only for an archival copy you intend to keep.
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