Photo Rejected for Wrong Dimensions: Pixels, cm and DPI Explained
Short answer
Only pixels are real — centimetres and DPI are a roundabout way of stating a pixel count. Divide the centimetres by 2.54 to get inches, then multiply by the DPI. So 3.5 × 4.5 cm at 200 DPI is 276 × 354 pixels. Crop to that ratio first, then resize to the exact pixel numbers.
On this page
A visa portal asks for a photograph “3.5 × 4.5 cm, 200 DPI, between 20KB and 50KB”. Your phone tells you the photo is 4032 × 3024. There is no obvious relationship between those two descriptions, and the upload fails with “incorrect dimensions”.
The relationship is one division and one multiplication. Once you have it, the requirement stops being mysterious.
The three units, and which one is real
Only one of these describes something actually inside your file.
Pixels are real. A digital image is a grid of coloured squares, and the pixel dimensions — 4032 × 3024 — are a count of that grid. This is the only measurement a web form can genuinely verify.
Centimetres and inches are not in the file at all. An image has no physical size until something prints it or displays it. A 276-pixel-wide image is 3.5cm wide when printed at 200 DPI, 2.3cm wide at 300 DPI, and 3.8 metres wide on a billboard. Same file every time.
DPI is the exchange rate between the two. It is a single number written into the file’s metadata saying “when printing, pack this many pixels into each inch”. It does not change a single pixel of the image.
That is the key insight. When a form says “3.5 × 4.5 cm at 200 DPI”, it is not describing two separate requirements. It is describing one requirement — a pixel count — in a roundabout way.
The arithmetic
Two steps:
- Centimetres to inches: divide by 2.54.
- Inches to pixels: multiply by the DPI.
Worked through for the common case:
Width: 3.5 cm ÷ 2.54 = 1.3780 inches
1.3780 × 200 DPI = 275.6 → 276 pixels
Height: 4.5 cm ÷ 2.54 = 1.7717 inches
1.7717 × 200 DPI = 354.3 → 354 pixelsSo the requirement is 276 × 354 pixels. Resize your photo to that and it will pass, regardless of what DPI tag the file carries.
If the measurement is already in inches, skip step one. A 2 × 2 inch photo at 300 DPI is simply 600 × 600 pixels.
Common requirements, pre-calculated
| Requirement | Inches | Pixels |
|---|---|---|
| 3.5 × 4.5 cm @ 200 DPI | 1.38 × 1.77 | 276 × 354 |
| 3.5 × 4.5 cm @ 300 DPI | 1.38 × 1.77 | 413 × 531 |
| 2 × 2 in @ 300 DPI (US visa) | 2 × 2 | 600 × 600 |
| 5 × 7 cm @ 300 DPI | 1.97 × 2.76 | 591 × 827 |
| 4.5 × 3.5 cm @ 600 DPI | 1.77 × 1.38 | 1063 × 827 |
| A4 full page @ 300 DPI | 8.27 × 11.69 | 2480 × 3508 |
| 3 × 4 cm @ 200 DPI | 1.18 × 1.57 | 236 × 315 |
Rounding half a pixel either way is fine. No validator checks to that precision.
Resizing to an exact pixel size
The complication is aspect ratio. Your photo is probably 4:3 or 3:2; the requirement is probably 3.5:4.5, which is 7:9. Resizing without accounting for that will either squash the image or leave it the wrong shape.
Crop first, then resize. This is the correct order:
- Crop the photo to the ratio of the target — for 276 × 354, that is a portrait crop slightly taller than it is wide. Most crop tools let you type a custom ratio or lock to one.
- Resize the cropped result to the exact pixel dimensions.
If you resize first, you have to squash or stretch to fit, and a stretched face is immediately obvious on an ID photo.
Our image compressor handles the resize step and shows the resulting file size, which matters because these forms usually impose a KB limit alongside the dimensions. Do the crop in your phone’s Photos app or Windows Photos first, then resize.
Doing it in built-in tools
Windows Paint: Resize → choose Pixels → untick Maintain aspect ratio → enter both numbers. Untick it only after cropping to the right ratio, otherwise you will distort the photo.
macOS Preview: Tools → Adjust Size. Set the units to pixels, enter the values, and leave Scale proportionally ticked if your crop already matches the ratio. The Resolution field here is the DPI tag; setting it with Resample Image unticked changes only the metadata.
IrfanView: Image → Resize/Resample, which has preset sizes and a DPI field in the same dialog.
Why “set it to 300 DPI” usually does nothing
This is the most common misunderstanding, and it wastes a lot of time.
Opening a photo, changing the DPI field from 72 to 300, and saving produces a file with identical pixels, identical appearance and identical file size. The only change is one number in the header.
Whether that helps depends entirely on what the form checks:
| What the form checks | Does changing the DPI tag help? |
|---|---|
| Pixel dimensions | No. Resize the actual pixels. |
| File size in KB | No. Compress or resize. |
| DPI metadata only | Yes, this is the rare case where it works. |
| Printed dimensions | Yes — but only if you have the pixels to back it up |
Some print-oriented submission systems genuinely do read the DPI tag and calculate a physical size from it. For those, setting DPI correctly matters. For a typical web upload form, it is irrelevant.
The reverse is also true: a photo your camera tagged as 72 DPI is not low quality. Phones write that number as a meaningless default. A 4032 × 3024 photo at “72 DPI” has more than enough pixels to print at 300 DPI across a 13 × 10 inch page.
Myths worth discarding
- “Higher DPI means better quality.” Only if the pixel count rises with it. Setting a 300-pixel image to 1200 DPI just instructs the printer to print it very small.
- “72 DPI is for screens, 300 DPI is for print.” The 72 figure comes from 1980s Macintosh displays and has been meaningless for decades. Screens today range from about 100 to over 400 pixels per inch, and none of them read the DPI tag.
- “Upscaling to the required size is fine.” Enlarging adds interpolated pixels, not information. A 150 × 200 photo stretched to 600 × 800 is a blurry 600 × 800 photo, and an ID photo reviewer will see it.
- “The file size requirement and the dimension requirement are the same thing.” They are independent checks. A photo can be the correct 276 × 354 and still be rejected for being 8KB when the minimum is 20KB.
If your photo is too small to start with
There is no honest fix. If the requirement is 600 × 600 and your source is 400 × 400, you need a better source — re-photograph, or find the original rather than a copy that someone resized for WhatsApp.
Photos sent over messaging apps are routinely downscaled to around 1600 pixels on the long edge and then cropped, which is why the version in your chat history is often too small while the original in your camera roll is fine.
If your photo is an iPhone HEIC file and the form will not even read it to check the dimensions, convert it first with the HEIC to JPG converter — a format rejection often surfaces as a vague dimension or upload error.
What to expect
Once you have converted the requirement to pixels, crop to ratio, resize to the exact numbers, and export as JPG. If a KB range is also specified, the exact-size compression method covers hitting it without blurring the result, and reducing an image for an upload limit covers the megabyte-scale version of the same problem.