How to resize a photo to an exact size: pixels, print size or file size

“Resize this photo” hides four different requests. A web page wants 1080 pixels across. A batch for a gallery wants every picture capped at 2048 on its long edge, portrait or landscape. A print shop wants 15 × 10 cm at 300 ppi. An application form wants the file under 100 KB. Each is a different rule, and a resizer that offers only one of them makes you do arithmetic it should be doing.

The four rules, side by side

You need	Set	Example	What comes out
A width or height on screen	Pixels	Width 1080	1080 × 1440 from a 3024 × 4032 portrait
A cap for a mixed batch	Longest side	2048	1536 × 2048 portraits and 2048 × 1536 landscapes
A physical print	Print size	15 × 10 cm at 300 ppi	1772 × 1181, with 300 ppi written into the file
An upload limit	Under, in KB	100	the highest quality at or below 100,000 bytes

Longest side is the rule people most often need and least often find. Set “width 2048” on a folder of phone photos and every portrait comes out 2048 wide and 2731 tall, taller than the landscapes beside it. A long-side cap treats both orientations the same.

Print size is arithmetic, and the file should remember it

Pixels per inch (ppi) is how many image pixels are laid along one inch of paper. The pixel count for a print is length ÷ 2.54 × ppi for centimetres: 15 ÷ 2.54 × 300 = 1771.65, so 1772 pixels, and 10 cm gives 1181. The pixel converter explains why other converters disagree with each other about this.

Getting the pixels right is half of it. Every image file has a field for its resolution, and a layout or print app reads it to decide how large to place the picture. None of the five online resizers we measured fills that field in: every file came back saying 72 with no unit. At 72 ppi, 1772 × 1181 pixels places at 62.5 × 41.7 cm, four times the intended width. The resize tool writes the ppi you chose into the JPEG or PNG header, so the photo places at 15 × 10 cm.

Landing under a file size

Forms and platforms state limits in KB or MB, and a file one byte over is refused. Two levers make a JPEG smaller: quality and pixel count. Lowering quality from 85 to 70 costs less visible detail than cutting pixels for the same saving, until blocking appears; below that point shrinking the picture is the smaller loss. So the tool searches quality first, between 30 and your chosen ceiling, halving the range each try, and only reduces the dimensions when quality alone cannot reach the limit.

Two details matter on a form. First, 100 KB is taken as 100,000 bytes, which also passes a form that counts 1,024 bytes to the kilobyte. Second, the result is either under the limit or flagged as not reachable; it is never handed over at 104 KB.

What goes wrong with phone photos

A phone stores a portrait photo sideways and adds an orientation tag that tells viewers to turn it. It usually records colour in Display P3, a wider gamut than the sRGB most of the web assumes, and it writes the GPS position into the file. Each of these trips a resizer that reads the stored pixels without reading the labels.

We sent one such photo through five online resizers on 8 October 2026, asking for 1080 pixels wide:

Tool	Came out	Colours	Location data
imageresizer.com	1080 × 1440	Shifted: profile dropped, red 220, 30, 30 became 202, 54, 44	Removed
iLoveIMG	810 × 1080, narrower than asked	Correct	Kept
simpleimageresizer.com	1440 × 1080, squashed to 4:3	Correct	Kept
bulkresizephotos.com	1080 × 1440	Correct	Removed
BIRME	1080 × 1440	Correct	Removed

The faults are one mistake made three ways: reading the size the file is stored at instead of the size it is shown at, or discarding the colour profile instead of converting it. The resize tool turns each photo by its tag, checks the result against the header, converts to sRGB, and says per file that the location data was removed.

Sharpness depends on the resampler

Resampling computes new pixels from old ones. Scored against a Lanczos3 reference on a test image built to show aliasing, Chromium’s canvas scored 21.33 dB at its default setting and 27.03 dB at “high”; Safari’s engine scored 21.37 dB whatever it was asked; the tool’s Lanczos3 pass scored 37.33 dB. The difference shows as shimmer on fine patterns and roof tiles. Light or strong sharpening is available after the resize, and is off by default because it cannot be undone.

Doing it in the resize tool

1. Open Resize image and press Choose images, or drop or paste files anywhere on the page. A sample phone photo is already loaded, marked as a sample, so you can see the preview first; your first file replaces it.
2. Under Size, pick Pixels, Longest side, Percent or Print size, and fill in the boxes (Print size asks for the Resolution in ppi there). With both width and height set, choose Fit inside or Fill and crop; with Fill, tap the photo to place the focal point.
3. Open More options only to change what its summary line says: JPEG, PNG, WebP (where your browser can write it) or Same as each file; Quality, or a size in Under; Resolution in ppi; sharpening; and Never make a photo larger than it is, ticked unless you want enlargements.
4. Press Resize (it counts the images: Resize 3 images). Each card shows the size reached in pixels and bytes, and the button becomes Download all 3 as .zip. Change a setting afterwards and the cards say so, and the button goes back to Resize.

Other ways to do it

On a Mac, Preview’s Tools → Adjust Size resizes an image, one file at a time. On Windows, the Photos app crops and rotates images. Neither sets a byte limit for you, so a file for a form still needs checking by hand.

Checking that nothing was uploaded

Open your browser’s developer tools on the Network tab before resizing. The resize engine and its encoders load from this site on first use; nothing carrying your photo is sent.

For a single photo that also needs cropping and turning by hand, use the image editor. To make one photo fit every social platform’s sizes, use social media image sizes.