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Image Resizer

Resize images by longest side, percentage or width and height, in your browser, with no upload.

By Nitin Raturi · Last reviewed

Input

How to use the Image Resizer

Change an image’s pixel size in your browser, by longest side, percentage or a box.

  1. Choose an image.
  2. Choose how to give the new size, and enter it.
  3. Choose the file type and, for JPEG or WebP, the quality.
  4. Check the new size and preview, then download.

Good to know

  • Nothing is uploaded.
  • To make a file smaller without changing pixels, use the image compressor.

Change an image’s pixel size by longest side, percentage, or width and height.

Runs in your browser. Nothing you type is uploaded or saved in the link.

Image

The picture to resize. It is opened in your browser and never uploaded.

How to fill it in

  • Choose a JPEG, PNG, WebP, GIF or BMP file up to 30 MB and 40 megapixels.

Resize by

How to give the new size.

How to fill it in

  • Longest side: one number for the longer edge; the other follows.
  • Percentage: scale both sides by the same amount.
  • Width and height: a box to fit inside, or exact pixels.

Example

A 4,000 × 3,000 photo becomes 1,280 × 960 at 1,280 on the longest side, or 2,000 × 1,500 at 50%.

Longest side (pixels)

The new length of the longer edge, in pixels.

How to fill it in

  • Enter a whole number from 1 to 10,000.

Save as

The file type of the resized image.

How to fill it in

  • JPEG: photos; transparent areas become white.
  • PNG: lossless and keeps transparency; larger files.
  • WebP: small and keeps transparency; some older apps cannot open it.

Quality

For JPEG and WebP, how much detail is kept. PNG is always lossless.

How to fill it in

  • Enter a whole number from 5 to 100. 90 keeps photos sharp.

Result

Choose an image to see the result here.

ChangelogHow we test this toolEmbed this tool

How this calculator works

  1. Step 1Open locallyNo uploadThe file is decoded on your device.
  2. Step 2New sizeW × HFrom the longest side, a percentage or a box.
  3. Step 3RedrawSmooth scalingThe picture is redrawn at the new size.
  4. Step 4SaveJPEG, PNG or WebPPreview, then download.

Resizing changes how many pixels the image has. Fewer pixels make a smaller file and a picture that loads faster; more pixels do not add detail and only make it softer.

Each side is rounded to the nearest whole pixel, and never below one pixel.

Worked example

A 4,000 × 3,000 photo with its longest side set to 1,280
Scale
longest side ÷ current longest side
  1. Scale1,280 ÷ 4,0000.32
  2. Width4,000 × 0.321,280
  3. Height3,000 × 0.32960
  4. New size1,280 × 960

At 50% instead, the same photo becomes 2,000 × 1,500.

Keep proportions or stretch

  • Keep proportions405 × 720Fits inside the box; nothing is distorted.
  • Stretch1,280 × 720Fills the box exactly; faces and shapes look squashed.

Read the result

The status line gives the new pixel size and file size, and warns when the image was made larger than the original.

The facts list compares the original and resized sizes. For exam-form photos with fixed pixel and KB limits, use the photo and signature resizer.

Assumptions and limits

  • PrivateNothing is uploaded; the image stays on your device.
  • Size limitsUp to 30 MB in, and 10,000 pixels a side and 40 megapixels out.
  • Metadata droppedCamera details and location (EXIF) are not kept.
  • Browser scalingUses your browser’s high-quality smoothing.

Animated GIFs are saved as a single still frame.

Resizing changes dimensions. File size and proportions have their own tools.

To reduce file size, use the image compressor. The aspect ratio calculator finds matching sizes, and the photo and signature resizer meets form rules.

Common mistakes

  • Mistake: Enlarging a small image to make it sharper.

    Instead: Use the original, larger file; enlarging adds no detail.

  • Mistake: Stretching a portrait photo into a landscape box.

    Instead: Keep proportions, or crop it first.

  • Mistake: Saving a photo as PNG to make it small.

    Instead: Use JPEG or WebP for photos; PNG suits graphics and screenshots.

Checking the method

Every golden size is recomputed by an independent script with exact fractions and half-up rounding.

The script solves the box fit by checking which side limits it, rather than taking the smaller of two ratios, and compares every size.

Read how we test our calculators, or browse more everyday tools.

Frequently asked questions

Is my image uploaded?

No. It is resized in your browser and saved straight to your device.

How do I resize a photo to a set width?

Choose Longest side or Width and height. A 4,000 × 3,000 photo with its longest side at 1,280 becomes 1,280 × 960.

How do I halve an image’s size?

Choose Percentage and enter 50. 4,000 × 3,000 becomes 2,000 × 1,500.

What does Keep proportions do?

It fits the image inside your width and height without distortion. A 1,080 × 1,920 frame in a 1280 × 720 box becomes 405 × 720.

Can I resize to a KB limit for a form?

Use the photo and signature resizer for exam forms, or the image compressor for a target file size.

Sources and methodology

The formulas are standard time-value-of-money results. We check every figure against golden values worked out independently, by closed form and by month-by-month simulation; see the methodology.

Written and maintained by Nitin Raturi, a software engineer (about the author). Last reviewed 3 Nov 2026; next review due by . Found an error? Tell us.

Changelog

  • : Initial release.

  • Image Compressor

    Make JPEG, PNG or WebP images smaller in your browser, by quality or to a target size, with no upload.

  • Aspect Ratio Calculator

    Find the aspect ratio of any width and height, and the matching height for a new width.

  • Image to PDF

    Turn photos, scans and screenshots into one PDF in your browser, with no upload.

  • Photo & Signature Resizer

    Resize and compress a photo or signature to the pixels and KB an exam or job form asks for, in your browser.