The signature rule that cannot be met as written
Twenty kilobytes is the usual ceiling for a scanned signature on recruitment and exam forms, and it rarely comes alone. The IBPS notice for 2026, for example, asks for a signature of “140 x 60 pixels (preferred)” with a file size “between 10kb – 20kb”. We saved a scanned signature at those exact pixels with Chrome’s JPEG encoder, and it could not reach the minimum at any quality:
| Signature saved at | Highest quality | Normal quality (0.92) |
|---|---|---|
| 140 × 60 px (the “preferred” size) | 4.3 KB | 3.4 KB |
| 280 × 120 px | 11.2 KB | 7.8 KB |
| 420 × 180 px | 21.1 KB | 13.8 KB |
| 708 × 236 px (6 × 2 cm scanned at 300 dpi) | 41.5 KB | 32.3 KB |
A signature is mostly white paper, and white paper compresses to almost nothing. At 140 × 60 there simply are not enough pixels to weigh 10 KB. The notice calls the pixel size preferred and the file size a range, so the range is the rule to keep: somewhere between 280 and 420 pixels wide, the same signature lands inside 10–20 KB.
Under 20 KB, or between 10 and 20?
“Under 20 KB” is the default: the tool finds the highest quality that fits and never makes a file bigger. If your form also gives a minimum, pick the 10–20 KB · signature preset or type the minimum yourself. A file that comes out too small is then enlarged step by step until it lands in the range, and the result says so. In our test a 140 × 60 signature of 4.0 KB came out at 343 × 147 and 10.5 KB. Enlarging adds no detail; it only gets the file past the floor.
Scanning a signature that fits first time
- Black pen, plain white paper. That is what the notice asks for, and ruled lines or a tinted page only give the compressor more to encode.
- Scan at 200–300 dpi, or photograph it in daylight with the page flat and no shadow of the phone across it.
- Crop close to the ink with Crop Image. The margin adds nothing and makes the signature smaller in the box on the form.
- Compress here. Our 708 × 236 scan came out at 19.1 KB and quality 0.85 at its full size, with no resizing needed.
If your signature looks faint or grey after scanning, that is the scanner’s exposure, not the compression. Rescanning with the page pressed flat usually fixes it better than any editing afterwards.
20 KB for a photo
A passport-style photo at 200 × 230 pixels fits under 20 KB at high quality: ours was 16.8 KB at the highest setting. A full phone photo has to shrink a long way to get there. Check the form first, because many that cap the signature at 20 KB allow the photo up to 50 KB, often with a 20 KB minimum; for that, use Compress Image to 50KB and its 20–50 KB preset.
20,000 bytes, not 20,480
A form can count a kilobyte as 1,000 or 1,024 bytes, and the page rarely says which. This tool aims for 20,000 bytes or less, which passes either way. Why a file your computer shows as under the limit can still be refused is explained in why a 500 KB file fails a 500 KB limit.
Your signature stays on your device
The signature is decoded, compressed and saved inside your browser. Nothing is uploaded, which matters more for a signature than for almost any other image you will put through a web tool.
How this was measured. On 30 September 2026, in Chrome 154, with the same canvas JPEG encoder this tool uses. The signature was a 6 × 2 cm test signature at 300 dpi with paper texture. Rule quoted from the IBPS CRP-PO/MT-XVI notification (30 June 2026); other forms use other ranges, so check yours.