Thumb Impression Resizer

A growing number of recruitment and entrance forms ask for a scan of your thumb impression along with the photograph and signature. The rules are not the same everywhere. Some bodies want a wide frame of about 3.5 by 1.5 centimetres, others a small square such as 240 by 240 pixels, and others a larger square of 300 by 300 pixels. File limits usually fall between 10 and 50 KB.

These starting values come from the sizes we saw for several exams, for example a wide frame for some state commissions, a 240 pixel square for bank recruitment and a 300 pixel square for national tests. Your own notice always decides. Use Custom or the Customise section to enter its exact numbers.

Most notices ask for the left thumb, and many say so in a single line. Some ask for the right thumb, and a few for a different finger. The resizing steps are identical for all of them, because the tool only changes the size of the picture. Make sure you press the correct finger on the pad and keep the notice open while you do it.

1. Prepare the ink. Use a fresh stamp pad. A dry pad gives a pale, broken print.
2. Press and roll. Press the thumb on the pad, then roll it gently across white paper from one edge to the other in one smooth motion.
3. Photograph it. Lay the paper flat in daylight and photograph it from straight above, with no shadow from your hand.
4. Upload and crop. Pick a size tab, upload the photo and centre the print in the frame.
5. Clean and check. Keep ink clean-up on, wait for the green ticks and download.

The ridges are the whole point of the picture, so a good print matters more than anything the tool can do afterwards. Too much ink fills the gaps between the ridges, and too little leaves the print broken.

• Light, even pressure. Pressing hard squashes the ridges together.
• One print only. Do not stamp twice on the same spot.
• Clean paper. Use plain white paper with no lines or marks.
• Dry first. Let the ink dry for a few seconds before you move the page.

Phone photos tend to make white paper look grey or yellow and ink look brownish. The ink clean-up switch turns the paper white and the print dark, which also makes the file smaller. The strength slider controls how aggressive this is. Start in the middle, and raise it only if the ridges look faint. If they start to fill in, lower it again.

A fingerprint is a high-contrast picture, which compresses well. The tool resizes to the pixel size first, then searches for the best JPEG quality that stays under your KB target. Choose Within range for a safe file just under the limit, or Exactly when the form wants a specific number. Leave the target empty if your form has no limit.

• The print is smudged, faint or has two overlapping impressions.
• The wrong thumb or finger was used.
• The file is outside the KB range or the pixel size is wrong.
• The picture was stretched instead of cropped.
• A shadow, ruled line or other writing is in the frame.
• The file is not a real JPEG.

A fingerprint is personal biometric data, so everything here happens inside your browser and the image is never sent to our servers. When the file is ready, download it or use Share to pass it on. Delete shared copies from chat apps afterwards, and do not post a fingerprint image publicly.