Resize and crop an image for the web, Instagram or YouTube

The notions to know: pixels, proportions, cropping

A digital image is a grid of pixels. Its size is given in pixels (width × height), not centimetres: on screen, “dpi” (dots per inch) is meaningless, only the pixel count matters. Dpi serves only for printing, to convert pixels into centimetres.

The width-to-height ratio is the proportion. Changing width and height independently distorts the image (a face too wide). To avoid that, you fix one dimension and let the other be calculated. To get a proportion different from the original (a 4:3 photo to a 1:1 square), you must crop, that is cut the edges, because you cannot fit a rectangle into a square without distorting it or leaving bands.

Resizing step by step with Resize Image

1. Drop one or more images (100 MB maximum each; above 100 megapixels the image is refused).
2. Choose the method: exact pixel dimensions, a percentage of the original size, or a preset (Instagram, Facebook, YouTube, HD, 4K…).
3. Leave “Keep proportions” ticked: enter the width and the height is worked out.
4. With a preset, “Fill” crops to the centre to get exactly the size you want; “Fit” keeps the whole image.
5. Pick the output format (JPG, PNG, WebP) and the quality, then download. The same setting applies to every image in a batch.

Resizing uses the high-quality Lanczos (pica) algorithm, sharper than a browser's simple preview.

The exact social media formats

With a preset in Resize Image, you can either crop to the centre to get exactly the size, or keep the whole image. JPEG is saved at 92% by default. Check the platform's current recommendations: these sizes change.

Cropping with Crop Image

Move the frame with the mouse or finger, resize it by its handles (44 px targets on touch screens), or nudge it pixel by pixel with the keyboard arrows. Preset ratios are offered (free, original, 1:1, 4:3, 3:2, 16:9, 21:9, 5:4, 3:4, 2:3, 9:16) and you can type X, Y, width and height in pixels for a precise cut, with zoom up to 400%. The orientation of phone photos is respected.

Working out the size needed for printing

For printing, count on 300 dpi. A 10 × 15 cm photo is 3.94 × 5.91 inches, about 1,181 × 1,772 pixels; an A4 page (21 × 29.7 cm) needs 2,480 × 3,508 pixels. An image 1,200 pixels wide printed 20 cm across drops to about 152 dpi: it will look less sharp. For the web, a display 800 pixels wide calls for 1,600-pixel files if you want to stay sharp on high-density screens.

Practical tips

• Reduce, do not enlarge. Reducing drops pixels with no visible loss; enlarging invents pixels and blurs the image. A warning tells you when a format forces enlargement.
• Crop first, resize afterwards: you lose fewer useful pixels.
• Keep the original and work on a copy.
• For a blog, 1,200 to 1,600 pixels wide is enough; follow up with compression (see Shrink an image's file size with no visible loss).

Common mistakes

• Stretching the image by hand to fill a frame, which squashes it.
• Confusing size in pixels with file weight: a 1,080-pixel image can weigh 100 KB or 5 MB depending on its quality.
• Cropping a portrait to a square and cutting off the top of the head: check the preview before confirming.
• Choosing PNG for a photo to publish: the file will be very heavy.

Honest limits

• Social network formats change: check the platform's current recommendations if in doubt.
• An image smaller than the target format will be enlarged (with a warning) but will not gain detail.
• The tool does not retouch content: no background removal, no automatic enhancement.

Frequently asked questions