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How to resize a signature for an online form, such as 10–20 KB at 140 × 60 pixels

A signature upload looks simple until the form says it’s too small, too large or the wrong shape. This is how to sign, capture and size it so it passes first time.

Signatures3 min readUpdated By the Anekvio team

Quick answer

Sign on plain white paper with a black or dark blue pen, take a flat, well-lit photo, and crop close around the signature. Resize it to the exact pixels in the instructions, for example 140 × 60, and save it as a JPG inside the size range, for example 10–20 KB. Small signatures often come out under the minimum, so check that limit too.

Signature size in KB, pixels and cm

Every form sets its own rules, so follow yours. A typical example, used by several Indian bank exam notices, is a JPG of 140 × 60 pixels at 10–20 KB. Other forms give the size in centimeters: at 200 DPI, 3.5 × 1.5 cm is 276 × 118 pixels.

Forms also commonly ask for black or dark blue ink on white paper, your full usual signature (sometimes not in capital letters), and the signature only, with no name under it, no lines and no stamps. Whatever you upload, sign the same way on any later documents.

1. Sign

  • Use plain, unlined white paper and a pen with a fairly thick, dark line, such as a gel pen. Thin ballpoint lines can fade when the image is made small.
  • Sign a little larger than usual, in a space about twice as wide as it is tall. A 140 × 60 shape is about 2.3 times as wide as it is tall.
  • Sign a few times and pick the clearest one.

2. Scan or photograph it

  • Scan it if you can. Otherwise take a photo in daylight, with the phone held flat, directly above the paper.
  • Avoid shadows from your hand or phone, and don’t use the flash, which causes glare.
  • Let the paper fill most of the frame, without using digital zoom.

3. Crop it

Crop close around the signature with a small, even margin, and match the shape the form wants. For 140 × 60 pixels, crop to a wide rectangle with the same proportions, so resizing doesn’t squash the letters.

4. Resize to the pixels and size range

  1. Resize to the exact pixels in the instructions.
  2. Save as JPG, and set the DPI if the instructions mention one.
  3. Check the size in KB. At 140 × 60 pixels, a clean signature on white paper can come out well under 10 KB.

Image size in pixels, inches, cm and DPI explains why this order works.

Signature must be at least 20 KB? How to fix it

If the form says the signature must be at least 10 or 20 KB, save it again from the original at a higher JPG quality; the pixels stay the same. Increase image size in KB saves it inside a range for you. More in how to increase photo size in KB.

Upload errors and their fixes

  • “Invalid dimensions.” The pixels don’t match exactly. Resize to the numbers in the instructions, after cropping to the same shape.
  • “Invalid file format.” The file is PNG, HEIC or WebP. Convert it to JPG rather than renaming it.
  • Refused later as unclear. The strokes were too thin or faint. Sign again with a darker pen, in better light.

Thumb impressions and handwritten declarations

Some forms also ask for a thumb impression or a handwritten declaration. The same method works: dark ink on white paper, a flat, well-lit photo, a close crop, then the exact pixels and size range. For a thumb impression, press firmly once and lift straight up, so the ridges don’t smudge.

Questions people ask

What is the standard signature size for online forms?

There’s no single standard; each form sets its own. A common example on Indian exam forms is a JPG of 140 × 60 pixels at 10–20 KB.

How do I resize my signature to 20 KB?

Crop it, resize it to the pixels the form asks for, and save it as a JPG at a quality that lands just under 20 KB. If it comes out too small, save at a higher quality.

What is 140 × 60 pixels in cm?

At 200 DPI it’s about 1.78 × 0.76 cm. The formula is cm = pixels ÷ DPI × 2.54.

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