Resize Image in cm and KB (JPG Format): 6 x 2 cm, 3.5 x 4.5 cm

To resize an image in cm and KB in JPG format, enter the width and height in centimetres, choose a DPI (200 for most online forms, 300 for printing), and set the maximum file size in KB. Our resize image in cm tool does all three in one go: it converts cm to pixels, writes the DPI into the JPG and compresses under your KB limit, all inside your browser.

The reason forms confuse people is that a digital image has no physical size by itself. It only has pixels. A "6 cm x 2 cm" instruction becomes a pixel size once you pick a DPI (dots per inch). Get that one idea and every cm instruction becomes easy.

How to resize an image in cm and KB (step by step)

1. Crop first if needed. If the photo has a lot of empty background, or the signature sits in the middle of a big sheet of paper, trim it with crop image. Resizing an uncropped image to 6 x 2 cm will squash or cut it.
2. Open resize image in cm and choose your file. It starts at 3.5 x 4.5 cm and 300 DPI.
3. Enter the width and height your notice asks for, and keep the unit on Centimetres (or switch to Millimetres or Inches).
4. Set the DPI. Use 200 unless the notice says otherwise or you plan to print. Use 300 for printing.
5. Pick how to fit. "Crop to fill" trims the edges to match the shape exactly. "Fit inside" keeps the whole image and adds white padding. "Stretch" distorts the image, so avoid it for faces.
6. Type the KB limit in "Max size (KB)", for example 50, and set the output format to JPG.
7. Download and check the file size and dimensions shown under the result.

If the form gives a KB range with a minimum (for example 20–50 KB), the exam photo resizer is the better choice, because it can also bring a too-small file up to the minimum.

cm to pixels: the one formula

pixels = cm ÷ 2.54 × DPI

There are 2.54 cm in an inch, so you convert cm to inches and multiply by dots per inch. Here are the sizes people search for most:

Values are rounded to the nearest pixel. Our longer explainer on image size, resolution and DPI covers the maths in more detail.

Resize image in cm with 300 DPI or 200 DPI?

Pick the DPI by where the image is going:

• Online forms: 200 DPI is common and keeps files small. A 3.5 x 4.5 cm photo at 200 DPI is easy to get under 50 KB.
• Printing: 300 DPI gives sharp prints at the stated size. Photo shops and home printers both expect it.
• Notice gives pixels too: If the notice says "3.5 x 4.5 cm (200 x 230 pixels)", trust the pixels and type them directly in resize image instead.

Changing only the DPI number in a file does not make an image sharper. Sharpness comes from the number of pixels in the original photo.

Resize image in cm without losing quality

Some quality loss is normal when you shrink a 12-megapixel phone photo to 276 x 354 pixels, but it should not look blurry. To keep it clean:

• Start from the original photo, not a WhatsApp-forwarded copy, which is already heavily compressed.
• Crop first, then resize. The face or signature then uses all the available pixels.
• Do not set the KB limit far below what the form needs. A 50 KB limit on a 276 x 354 px photo leaves plenty of room for good quality.
• Use JPG for photos. PNG photos get large and many portals reject them.

Signature in 6 cm x 2 cm

Signatures are the most common "cm" request after photos. Sign in black ink on plain white paper, photograph it in daylight, and crop tightly so very little paper shows. Then resize to 6 x 2 cm at 200 DPI with a max size of 20 KB (or whatever your notice says). If the paper looks grey, run it through black and white image with higher contrast first. Our guide to making a signature clear for online forms has more tips.

How to resize an image in cm in Paint

Windows Paint can resize, but only in percentage or pixels, not cm. To use it:

1. Work out the pixels with the formula above (for 6 x 2 cm at 200 DPI: 472 x 157).
2. Open the image in Paint and choose Resize on the Home toolbar (or press Ctrl+W).
3. Select Pixels, untick "Maintain aspect ratio" if you need an exact shape (crop first so it is not distorted), and type the values.
4. Save as JPEG.

Paint has no JPEG quality or KB setting, so you cannot aim for a specific KB in Paint. If the result is too big, run it through compress image to 50 KB or the right KB target afterwards.

How to resize an image in cm on a Mac

Preview on a Mac does support centimetres. Open the image in Preview, choose Tools > Adjust Size, set the unit to centimetres, enter the width and height, and set the resolution (in pixels per inch). Then use File > Export, pick JPEG and lower the quality slider if you need a smaller file. Preview shows the resulting file size in the export dialog.

Resize image in cm on a phone

You do not need an app. Open resize image in cm in Chrome or Safari, choose the photo from your gallery, enter the size, and download. On iPhone, if the photo is HEIC the tool reads it directly, and the output is a normal JPG that forms accept.

Common mistakes

• Stretching instead of cropping. A 4:3 phone photo forced into 6 x 2 cm with "Stretch" looks squashed. Crop first, or use "Crop to fill".
• Mixing up width and height. Forms almost always list width first. 3.5 x 4.5 cm is a tall portrait, not a wide one.
• Uploading the original by mistake. The resized file is named with its new pixel size, so pick that one.
• Going below the KB minimum. If the portal says 20–50 KB, a 9 KB file fails too.
• Using 72 DPI. Some old guides suggest it. At 72 DPI, 3.5 x 4.5 cm is only about 99 x 128 pixels, which looks poor and may be rejected for being too small.

Questions