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How to meet photo, signature and document size limits on online forms
Application forms for exams, jobs, admissions and bank KYC reject uploads that break their rules, often with a vague error. The rules are usually a mix of file size in KB, dimensions, and format. Here is how to read them and meet each one.
Every form sets its own rules, and they change between years. Always follow the official notification for the form you are filling. The numbers below are examples to show the method.
The four kinds of rule
| Rule | Example wording | What it means |
|---|---|---|
| File size | "between 10 KB and 50 KB" | Both a minimum and a maximum; too small is rejected too |
| Dimensions | "200 × 230 pixels" or "3.5 cm × 4.5 cm" | The shape and resolution of the image |
| Format | "JPG/JPEG only", "PDF only" | The file type; .jpg and .jpeg are the same thing |
| Content | "white background", "signature in black ink" | What should be in the picture |
File size in KB
1 KB is 1,024 bytes on most systems, though a few use 1,000. That small difference matters only when you are right at the limit, so aim a little under. Compress image and Compress PDF both stay strictly below the target you pick.
If a form has a minimum, such as 10 KB, and your file comes out below it, choose the next bigger target. A very small file usually means very few pixels, which is often the real reason it is rejected.
Pixels, centimetres and DPI
Forms that give sizes in centimetres usually also give a resolution in DPI (dots per inch), or expect one. To get pixels:
pixels = centimetres ÷ 2.54 × DPI
| Printed size | At 200 DPI | At 300 DPI |
|---|---|---|
| 3.5 × 4.5 cm (common passport-photo size) | 276 × 354 px | 413 × 531 px |
| 2.5 × 3.5 cm | 197 × 276 px | 295 × 413 px |
| A4 page, 21 × 29.7 cm | 1654 × 2339 px | 2480 × 3508 px |
When a form gives exact pixels, the shape matters as much as the size: 200 × 230 px is slightly taller than it is wide. Crop your photo to that shape in your phone's gallery (most editors have a free-ratio crop) before compressing. In size-target mode the compressor keeps the shape you give it and chooses the dimensions itself.
The photograph
- Plain, light backgroundA white or light wall, evenly lit. Shadows behind the head are a common reason for rejection.
- Face the cameraHead and shoulders, both ears visible if the form asks, no cap or dark glasses.
- Crop to the required shapeLeave a little space above the head.
- Compress to the limitPick the target just under the maximum. In our test, a 3000 × 2000 px photo reached 28.8 KB at 1100 × 733 px under a 50 KB target.
The signature
- Sign on plain white paperBlack or blue ink, as the form asks, a little larger than usual.
- Photograph in daylightStraight above, no shadow of your phone on the paper.
- Crop tightlyJust the signature with a small margin. Extra white paper wastes pixels.
- CompressSignatures are mostly white and compress very well. Our 1600 × 600 px signature reached 18.2 KB under a 20 KB target while keeping 1400 px of width.
Documents such as certificates and ID proofs
- If the form wants a PDF, turn photos into one PDF with JPG to PDF, or combine existing PDFs with Merge PDF.
- Then compress to the limit. Combine first and compress last: compressing once gives better quality than compressing pieces and then merging.
- If the limit is per file and too tight for a multi-page document, check whether the form accepts several uploads, and split it.
Checklist before you press upload
- Right format (.jpg or .pdf as asked), and the file opens on your phone.
- Size between the minimum and maximum.
- Dimensions or shape as specified.
- Readable: zoom in on the smallest text or the signature and check it.
- Right file in the right box: photo in the photo field, signature in the signature field.
Questions people ask
The form says JPEG and my file is .jpg. Will it work?
Yes. JPG and JPEG are the same format. If a form insists on the exact extension, you can rename the file.
My photo is a PNG or from an iPhone (HEIC). What do I do?
Open Compress image, set "Save as" to JPG and choose the size target. If your browser cannot open HEIC, set the iPhone camera format to "Most Compatible" or share the photo as JPG.
Why does the form say my file is invalid even though the size is right?
Usually the dimensions or format are off, or the file is a renamed type (a PNG renamed to .jpg). Re-save it as a real JPG with Compress image.