Plainwren

Image resizer

Change the width and height of JPG, PNG and WebP images: in pixels, as a percentage, or in centimetres, millimetres or inches at a DPI for print and form uploads. Resize one photo or a whole batch; everything happens on your device.

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How it works

Your browser opens each image, draws it at the new size on an invisible canvas and saves it again. Big reductions are done in halving steps, which keeps edges and text sharper than one big jump. Nothing is uploaded, so there is no limit on how many images you resize beyond your device's memory.

  • Pixels: type a width, a height or both. With one box empty, the other side is worked out so the picture keeps its shape.
  • Percent: 50% halves both sides, so the image has a quarter of the pixels.
  • cm, mm or inches: pixels = size in inches × DPI (1 inch = 2.54 cm). The DPI is also written into JPG and PNG files, so a printer or a form that reads it shows the right physical size.
  • Both sides set: "Fit inside" keeps the whole picture within the box; "Fill and crop" covers the whole box and trims the edges, centred; "Stretch" uses the exact size even if the picture looks squashed.

Worked examples

  • Phone photo for a website: a 4000 × 3000 photo resized to 1200 pixels wide becomes 1200 × 900, about 9% of the original pixels, so the file is usually far smaller too.
  • Fit inside Full HD: the same photo into 1920 × 1080 with "Fit inside" becomes 1440 × 1080, because the height reaches the limit first (3000 × 0.36 = 1080).
  • A 3.5 × 4.5 cm photo at 300 DPI: 3.5 ÷ 2.54 × 300 = 413 pixels wide and 4.5 ÷ 2.54 × 300 = 531 pixels tall. From a landscape photo, "Fill and crop" keeps the centre and trims the sides.

Forms often state a size in pixels or KB as well as in cm. Check the exact rules of the form or office you are applying to: this tool sets the size, it does not check that a photo meets an official photo standard.

Limits

  • Enlarging cannot add detail, so a small image made bigger looks soft. Tick "Never make images larger" to avoid it.
  • Metadata is removed (camera details, GPS), and photos are turned the right way up first.
  • File size in KB depends on the picture, not only on its dimensions. To hit a target such as 100 KB, use the image compressor; to change the format only, use the image converter.
  • HEIC, TIFF and SVG are not supported. Animated images keep only the first frame. The largest output is 16,384 pixels per side and 50 megapixels.

FAQ

How do I resize an image without losing quality?

Making an image smaller always removes pixels, but it stays sharp: use PNG, or JPG or WebP at quality 90 or more. Avoid making images larger than the original, which makes them look blurry.

How do I resize a photo to a size in cm?

Choose "cm, mm or inches", enter the width and height in cm and a DPI (300 for print), and pick "Fill and crop" if the photo has a different shape from the size you need.

What DPI should I use?

300 DPI is the usual figure for printed photos and many form uploads; 150 is enough for documents viewed on screen. DPI only links pixels to a physical size; on screen, the pixel count is what matters.

Can I resize many images at once?

Yes. Choose or drop several images; they all get the same settings, each gets its own download link and you can download them all as one ZIP.

How do I keep the aspect ratio?

Fill in only the width or only the height, or keep "Keep aspect ratio" ticked with "Fit inside" when you set both.

Are my photos uploaded?

No. Resizing happens in your browser and the images are not uploaded or stored.