Resize Image in Pixels, cm & KB Free

Resize Image in Pixels, cm and KB Online — Free

To resize an image, enter the width and height in pixels or cm, choose a DPI, set a KB range if your form has one, and tap Resize. For example, 3.5 × 4.5 cm at 300 DPI gives 413 × 531 pixels. Nothing is uploaded.

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How to resize an image in pixels, cm or KB

1Select or drop your image into the upload box.

2Enter the width and height, and choose pixels or centimetres.

3Leave Keep proportions on, or turn it off to centre-crop to the exact shape.

4Tap a DPI chip (72, 96, 150, 200 or 300) and add a minimum or maximum KB if the form asks for one.

5Tap Resize and download the JPG.

Key facts

Documently Resize Image is a free tool that sets the exact width and height of a photo in pixels or centimetres, writes a DPI value into the JPG and keeps the file inside a minimum and maximum KB range, all in one step. Centimetres convert to pixels with the formula pixels = cm ÷ 2.54 × DPI. For example, a 3.5 × 4.5 cm passport-style photo is 276 × 354 pixels at 200 DPI and 413 × 531 pixels at 300 DPI. In our tests, a 5.6 MB phone photo resized with the passport preset came out at 413 × 531 px, 300 DPI and 54 KB. With Keep proportions off, the photo is centre-cropped to the new shape instead of stretched. A file below the minimum KB is padded without changing the picture. Resizing runs in the browser canvas, so the photo is never uploaded. Enter the pixels or cm printed on your form, set the KB range, and tap Resize.

Forms rarely ask for just one thing. They want a photo of 200 × 230 pixels, under 50 KB, sometimes at 200 DPI, or a size written in centimetres. This tool handles all of it together: exact dimensions in pixels or cm, the DPI value in the file, and a KB range. It runs in your browser, so it works on any phone without installing an app.

When do you need to resize an image to exact dimensions?

Recruitment and exam forms that list photo and signature sizes in pixels, like 200 × 230 px.
Admission forms and certificates that give sizes in cm, such as 3.5 × 4.5 cm.
Passport-style photos for ID cards, hostel forms or bank account opening.
Shrinking a 4000 × 3000 pixel phone photo so it loads quickly on a website or email.

Pixels, cm and DPI explained in one minute

Pixels are what the screen and the portal actually check. Centimetres only make sense together with DPI (dots per inch), which says how many pixels fit into each inch when printed.

The formula is pixels = cm ÷ 2.54 × DPI, because 1 inch is 2.54 cm. So 3.5 cm at 200 DPI is 276 pixels, and 4.5 cm at 200 DPI is 354 pixels. At 300 DPI the same photo would be 413 × 531 pixels.

The same maths works in reverse: a 300 × 100 pixel signature at 200 DPI prints at about 3.8 × 1.3 cm.

The DPI you pick is written into the JPG header, which some portals read when they check the size in cm.

Tips and common rejection reasons

Stretched faces: turning off Keep proportions here centre-crops instead of stretching, so faces never look squashed. Check the crop still shows your full face.
File too small: some portals reject files under 10 or 20 KB. Set a minimum KB and the tool safely pads the JPG to reach it without changing the picture.
File too large: set a maximum KB and the tool lowers JPEG quality until it fits.
Upscaling a tiny image makes it blurry. Start from the original camera photo, not a WhatsApp forward or a screenshot.
Photo in PNG or WebP? The output is always JPG, the format most application forms ask for.

Private by design: nothing is uploaded

Resizing, cropping and re-encoding all happen in your browser using its built-in canvas. Your photo stays on your phone or computer, and the result is saved directly to your downloads.

We keep only anonymous counts, like which tool was used and the file size. No images, names or personal details are ever stored.

Frequently asked questions

How do I resize a photo to 3.5 × 4.5 cm?

Choose centimetres, enter 3.5 for width and 4.5 for height, pick 200 or 300 DPI, and tap Resize. At 200 DPI you get 276 × 354 pixels; at 300 DPI, 413 × 531 pixels. Check which DPI your form asks for, if any.

How do I resize an image to exact pixels and under 50 KB?

Enter the width and height in pixels, set the maximum KB to 50, and tap Resize. The tool first sets the exact dimensions, then adjusts JPEG quality to stay under 50 KB. Add a minimum KB too if the form has a lower limit.

Will my photo get stretched if I change both width and height?

No. With Keep proportions on, the other side adjusts automatically. If you turn it off to get an exact shape, the tool centre-crops the extra area instead of stretching, so your face or signature keeps its natural proportions.

What DPI should I choose for an online form?

Use the DPI the form mentions. If it gives only pixels, DPI does not change how the photo looks on screen, so any value works. If it gives cm without DPI, 200 or 300 DPI are common choices for clear passport-style photos.

Why is my resized photo bigger in KB after making it smaller?

File size depends on JPEG quality and image detail, not only on dimensions. A heavily compressed original can grow when saved at higher quality. Set a maximum KB value and the tool will keep the output under it.