Photo dimensions, pixels and print size
Work through the numbers and avoid using a print-sized crop where an original digital photo is required.
All photo guidesReviewed
35 × 45 mm
Physical print size
413 × 531 pixels
At 300 pixels per inch
Separate physical size, pixels and file size
A 35 × 45 mm photo describes the physical rectangle on paper. A 413 × 531 pixel image describes the number of picture samples in a file. A file size such as 200 KB describes how much storage that file uses. These measurements answer different questions, and changing a filename does not change any of them.
PhotoID Studio’s size presets are primarily a framing and print-layout starting point. A preset name alone does not establish that the exported JPEG satisfies an online application’s pixel dimensions, compression limit or permitted editing rules. Check those requirements separately before choosing an output.
Calculate the pixel grid for a print
For an image intended to print at 300 pixels per inch, use pixels = millimetres ÷ 25.4 × 300, then round to a whole pixel. A 35 mm width becomes about 413 pixels; a 45 mm height becomes about 531 pixels. These are rounded sample counts, not a second set of physical requirements.
The same calculation explains the sheet export. Six inches across at 300 pixels per inch is 1,800 pixels; four inches high is 1,200 pixels. The application arranges the selected photo inside that landscape sheet. This is why a printable sheet is a different file from the single-photo export.
| Example | Calculation | Pixel grid |
|---|---|---|
| 35 × 45 mm crop | 35 ÷ 25.4 × 300; 45 ÷ 25.4 × 300 | 413 × 531 |
| Exactly 2 × 2 inches | 2 × 300 on each side | 600 × 600 |
| 6 × 4 inch sheet | 6 × 300; 4 × 300 | 1,800 × 1,200 |
A print crop is not automatically an online upload
The UK digital passport guidance provides a useful example: it specifies at least 600 × 750 pixels and tells people using their own device not to crop the photo themselves. A 413 × 531 print crop falls below those pixel dimensions, even though 35 × 45 mm may look like the familiar printed format. Follow the online application’s capture and upload process in that case.
For a different authority, check its own digital instructions rather than carrying that UK example across. Write a short checklist: original or edited file, required width and height, permitted format, minimum and maximum file size, and any crop instructions. This tool does not currently provide a target-KB compression control, so do not assume an export will meet a portal’s file-size limit.
A resolution label cannot control your printer
An image can carry a resolution tag, but the printing application can still resize it. The exported sheet is designed for a 6 × 4 inch print. If software stretches the same file across a larger page, the individual photos become larger too. Always check the requested physical output size, regardless of the DPI label displayed by an image viewer.
Equally, increasing the pixel count cannot restore detail missing from a tiny source. If the usable face area of an original contains only about 150 pixels across, enlarging it to 600 pixels spreads that information over more samples. It does not give the camera a second opportunity to record eyelashes or skin detail. Choose a better original when sharpness is the issue.
Choose and verify the download
Use the single-photo download when you need one image and the receiving process permits that crop. Use the sheet download when you intend to order a measured paper print. Open the saved file, inspect its dimensions in your device’s file information and compare them with your checklist before submitting or paying for printing.