Resize Image in cm

The form says the photo must be 3.5 × 4.5 cm, or the signature 6 × 2 cm, and an image on a phone has no centimetres at all, only pixels. The missing number is the DPI, dots per inch, which says how many pixels make up an inch of the printed size. Choose it, and the centimetres turn into an exact pixel size. This page does that conversion, resizes the photo to it, keeps it under a KB limit and writes the DPI into the file.

How to resize an image in cm

1. Choose the photo at the top of the page.
2. Type the width and height in centimetres. The page opens at 3.5 × 4.5 cm; change them to what your form states.
3. Pick the DPI under "DPI written into the file". It starts at 200.
4. Set the KB limit, and a minimum if the form gives a range.
5. Press Download JPG. The result shows the pixels, the DPI and the bytes.

If the photo's shape differs from the frame, choose "Crop to fill" to cut the edges, or "Fit whole photo (white edges)" to keep all of it.

From centimetres to pixels

An inch is 2.54 cm, so:

pixels = centimetres ÷ 2.54 × DPI

The tool rounds to the nearest whole pixel. For the common 3.5 × 4.5 cm photo:

Doubling the DPI doubles each side and so roughly quadruples the pixels, and with them the bytes the file needs. A form that states both a size in centimetres and a KB limit has, in effect, also chosen how much detail the picture can carry.

The cm sizes Indian forms state

The IBPS and SBI notices state their photo and signature in pixels instead: 200 × 230 and 140 × 60 pixels preferred, with 200 DPI for the thumb impression and the declaration. When a form gives pixels, type them with "Pixels" selected rather than converting. For those exact presets, the Image Resizer in KB carries them, and the Signature Resize page sets the SSC signature and cleans up the paper as well.

Millimetres and inches

Forms do not always use centimetres. Convert first, then type centimetres, or type pixels directly:

Millimetres divide by ten. Inches multiply by 2.54 for centimetres, or by the DPI for pixels directly, which avoids rounding: 2 inches at 300 DPI is exactly 600 pixels. For a size like 5.08 cm, entering the pixels with "Pixels" selected gives the exact number without rounding.

Choosing a DPI when the form is silent

Many forms give centimetres and no DPI. Then the choice is about what happens to the file next.

For an upload that is only viewed on screen, 200 DPI is enough. A 3.5 × 4.5 cm photo at 200 DPI is 276 × 354 pixels, larger than most portals display it, and its file is small: 10,744 bytes in our test.

For a photo that will be printed, 300 DPI is the usual print standard. The same photo is 413 × 531 pixels, and our test file was 25,326 bytes, still under most limits.

Higher than 300 rarely helps. At 600 DPI the 3.5 × 4.5 cm photo needs 827 × 1,063 pixels, and under a 20 KB limit our test had to drop to 71% quality to fit. A form with a small KB limit and no DPI is better served by 200 or 300 DPI at high quality than by 600 DPI at low quality.

What happened in our tests

We used a 3,000 × 4,000 portrait of our own, 3.63 MB, with a plain light background:

Three things show here. A fixed size in centimetres keeps its pixels: when the KB limit is tight, the quality drops instead, as in the 600 DPI row, where 827 × 1,063 pixels went to 71% to fit under 20 KB. A loose limit is not filled: at 300 DPI the photo needed only 25,326 bytes, so a 200 KB limit changed nothing. And a small, plain photo can fall below a form's minimum; type the minimum and the tool raises the file into the range, as the Increase Image Size in KB guide describes.

The last row is the 2 × 2 inch size, typed as 5.1 cm: 5.1 cm is 5.08 cm rounded, which gives 602 pixels at 300 DPI instead of 600. For a size given in inches, multiply by the DPI and type the pixels.

What DPI does and does not do

The DPI is stored in two density fields of the JPEG header, which the JFIF standard defines. A form's checker or a print shop reads it to know the intended printed size; a phone gallery and a browser ignore it.

Changing the DPI adds no detail. At a fixed size in centimetres, a higher DPI means more pixels, so the picture is resized to a larger grid. If the photo you start from is smaller than that grid, the extra pixels are guessed from their neighbours. Our 3,000 × 4,000 portrait had far more pixels than any row above needed, so every result was a reduction.

The page also works as a DPI converter. Choose "Keep the photo's shape" and a DPI, and the tool writes that DPI into the file. The pixels stay as they are if the photo fits under the KB limit, and shrink if it does not.

Common mistakes with sizes in centimetres

Swapping width and height. A passport-style photo is taller than it is wide, so 3.5 × 4.5 cm means 3.5 cm across and 4.5 cm up. Typed the other way round, the tool makes a landscape frame and crops the face to fit it.

Changing the DPI after the form fixed it. If the notice states 200 DPI, choose 200 even when 300 looks better. A checker that reads the DPI field compares it with the notice, and a different number can be refused even though the picture is fine.

Expecting the printout to match by itself. Many print dialogs scale an image to the paper unless told not to. When you print the result, choose actual size or 100% scale, so the printer uses the DPI in the file.

What this tool assumes

• Pixels are centimetres ÷ 2.54 × DPI, rounded to the nearest whole pixel, between 8 and 8,000 on each side.
• The DPI you choose is written into the JPEG's density fields.
• The KB limit is a maximum met at X × 1,000 bytes or fewer; an optional minimum is met at X × 1,024 bytes or more.
• "Crop to fill" cuts the photo to the frame's shape, and the frame can be moved; "Fit whole photo" adds white edges.
• The photo stays on your device, and the saved JPEG carries no location or camera details. The tool has no link with any exam body or PAN agency, and notices change each cycle.