Why is my signature 'too small' for a 10 KB to 20 KB limit, and how do I fix it?

You photographed your signature, resized it to 140 × 60 pixels as the form asks, and the portal refused it: the file must be between 10 KB and 20 KB. Yours is 3 KB. You save it again at the highest quality. It is still about 3 KB.

You have not done anything wrong. A small, clean signature simply does not contain 10 KB of information, and no quality setting will change that.

Where the 10 to 20 KB rule comes from

The SBI guidelines also ask for the signature in black ink on white paper.

Why a clean signature is so small

A JPG is small when the picture is simple, and a signature is about as simple as a picture gets: a few dark strokes on a flat white background. At 140 × 60 there are only 8,400 pixels in the whole thing, most of them plain white.

These are the sizes we measured at the highest JPG quality:

At 140 × 60, neither version reaches 10 KB.

Why grey paper is not the fix

It is tempting to leave the shadow in, since it makes the file bigger. It does not work. At 140 × 60 even the grey version stopped at 6.9 KB, still under the minimum. The guidelines ask for white paper. And grey paper makes thin strokes harder to read at this tiny size.

So clean the paper first, and deal with the size honestly.

What "blank data inside the file" means

A JPG file is made of sections. One kind is a comment section, a part of the JPG standard meant for notes, which every picture viewer skips when it draws the picture.

When a clean signature comes out under the minimum, Resize Image adds a comment section filled with blank data. The file ends up a little over the minimum and never over the maximum. The strokes, the pixels and the colours are exactly what they were; open the file in any viewer and you see the same signature.

The tool always says when it has done this, in words like: "The picture itself came to 3.0 KB, so blank data was added inside the file to reach the 10 KB minimum. The picture is unchanged."

Some tools instead stick zeros on after the end of the picture. We use a comment section because the file stays a normal, valid JPG from start to finish. We have not tried it against every portal, so we will not promise that every one of them accepts it; what we can say is that it is a standard part of the format.

Step by step

1. Sign on plain white paper in black ink. Photograph it from straight above in daylight, with no shadow from your phone or hand, or scan it.
2. Open Signature Resize. It opens set for 10 to 20 KB, with Picture on Signature and Background on White. If your form also gives a pixel size, type it: for the bank exams, 140 in Width and 60 in Height.
3. Add the photo. The clean-up is on: the paper becomes white, the ink darker, and Trim to the signature cuts the picture to the signature with a small white margin. For grey or shadowed paper, choose White, fully. Under More options, Ink lets you keep the ink colour or make it black.
4. Read the preview: size in KB and exact bytes, pixels, JPG, and the name signature.jpg. If blank data was added, a note says so and tells you the size of the picture itself. Tap Actual size to check the strokes.
5. Tap Resize picture, download, and upload that file as it is.

If the signature does not fill the form's shape, the tool adds white edges rather than cutting into your strokes. White on white paper does not show.

Why the signature was rejected

• Under 10 KB. A clean signature is naturally this small. Let the tool fill it up, and keep Save as on JPG: a PNG or WebP cannot be filled.
• Over 20 KB. A large, grey signature. Set Background to White or White, fully, or set Colour to black and white.
• Wrong pixel size. 140 × 60 means exactly that, not 141 × 60.
• Rounding. A file your computer shows as 9.9 KB may be 10,100 bytes, and the portal may count differently. See KB vs KiB.
• Grey or shadowed background, or faint ink. The clean-up fixes both; for a heavy shadow, choose White, fully.
• Strokes cut off at the edges. Trim to the signature leaves a margin; if you crop by hand, leave some white around the ink.

What the tool cannot do

It cannot straighten a slanted signature or fix a smudge: sign again and retake the photo with the phone held level. It cannot turn a PNG into a padded file; keep Save as on JPG. And it cannot tell you whether a particular portal inspects the inside of the file. If your notice says anything specific about how the file must be made, follow the notice.