Image Resizer

Choose an image, set a new width or height in pixels (or a scale percentage), and download the resized copy. The aspect ratio stays locked unless you unlock it, and every pixel is processed on your device with the canvas — nothing is uploaded.

Choose an image, set the size, then press Resize image.

How resizing works

Resizing changes the number of pixels in an image. This tool draws your picture onto an HTML <canvas> at the new dimensions; the browser's built-in bilinear scaler interpolates the pixels, then the canvas exports a fresh PNG (or the original format) you can download.

new height = original height × (new width ÷ original width)

When Keep aspect ratio is on, setting either width or height computes the other side with the ratio above, so the image never looks stretched. A scale percentage simply multiplies both sides by that fraction.

Worked example

A 4000 × 3000 photo you want 1000 px wide:

Ratio: 1000 ÷ 4000 = 0.25.
Height: 3000 × 0.25 = 750 px.
Result: a 1000 × 750 image, one-sixteenth the pixel count, far smaller in file size.

Quality and formats

Making an image smaller looks clean; making it much larger than the original cannot add detail and will look soft, because the browser invents in-between pixels. PNG, JPG, GIF and WebP all load; the download is a PNG by default to preserve quality without re-compression artefacts. Because everything happens on the canvas in your browser, your photo is never sent to a server.

Tip: need to crop instead of scale? Use the image cropper, or turn an image into a data URI with the image to Base64 converter.

Frequently asked questions

Is my image uploaded anywhere?

No. The file is read locally and drawn onto a canvas in your browser. Nothing is sent to a server, so it is safe for private or unreleased images.

How do I keep the proportions?

Leave Keep aspect ratio ticked and set only one dimension — the other is calculated automatically so the image never looks stretched. Untick it to set both sides independently.

Can I make an image bigger?

You can, but enlarging beyond the original size cannot add real detail; the browser interpolates new pixels and the result looks soft. Downsizing always looks sharper.

What format is the download?

The resized image downloads as a PNG, which is lossless, so repeated edits do not accumulate compression artefacts. The original file is never modified.

MB
Mustafa Bilgic · Editor, Calcool
Resizes with the HTML canvas drawImage scaler. Everything runs in your browser - nothing you enter is uploaded, logged or stored.

Related calculators

✂️ Image Cropper🖼️ Image to Base64🧩 Base64 to Image🎨 Color Picker