Image
Resizer
Resize images to any dimension. Lock aspect ratio, use presets, and download instantly. 100% client-side.
Drop an image here or click to upload
PNG, JPG, WebP, GIF, AVIF
How It Works
Upload
Drop or select any image file from your device.
Resize
Set custom dimensions, scale by percentage, or pick a preset.
Download
Preview the result and download your resized image instantly.
Resize images online to exact pixel dimensions or by percentage, with optional aspect ratio lock to prevent distortion. ConverterUp's image resizer is useful for preparing photos for blog posts, e-commerce listings, profile pictures, or printable assets that require a specific size. Drop a PNG, JPG, WebP, or AVIF file, type your target width and height, and download the result in seconds. The resizing runs entirely in your browser, so original photos and any sensitive content never leave your device or get queued on a remote server.
Target sizes for social, web, and print
Open Graph / Twitter cards: 1200 × 630 is the universal safe size for link previews on LinkedIn, Facebook, Twitter/X, Slack, and Discord. Slack still crops at 1200 × 627, so keep critical content inside a centered 1200 × 600 safe area.
Instagram: feed posts 1080 × 1080 square or 1080 × 1350 portrait; Stories and Reels 1080 × 1920 (9:16). YouTube thumbnails: 1280 × 720. TikTok: 1080 × 1920. LinkedIn cover: 1584 × 396.
Web favicons: ship a 32 × 32, 180 × 180 (Apple touch), and 512 × 512 (PWA) at minimum. For retina displays, export at 2× the CSS pixel dimensions and let the browser downscale — a button that displays at 200 × 50 CSS pixels should be a 400 × 100 image.
Print: photographic print at 300 DPI means an A4 page needs roughly 2480 × 3508 pixels; a 6 × 4 inch postcard needs 1800 × 1200. For posters viewed from a distance, 150 DPI is acceptable. Always export print masters as PNG or TIFF, not JPG.
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Aspect ratio, cropping, and content-aware fits
When the target dimensions match the source aspect ratio, resizing is a pure scale. When they do not, you must choose: letterbox (preserve the whole image, add padding), crop (preserve the aspect ratio, trim edges), or stretch (distort the image to fit). Stretching is almost always wrong unless you are creating an intentional effect.
For portraits and product shots where the subject is centered, a simple center crop works. For landscapes and group photos, a center crop often cuts off important content — manually adjust the crop anchor, or pre-crop in an image editor before resizing.
The aspect ratio lock in the resizer prevents accidental distortion: change one dimension and the other follows. Turn it off only when you genuinely want to squash or stretch (rare), and verify with the live preview that the result still reads correctly.
For e-commerce catalogs, decide on a single canonical aspect ratio (4:5 portrait is popular) and crop every product photo to that ratio before resizing. Inconsistent aspect ratios across a grid look amateurish and break responsive layouts.
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Resampling algorithms and quality
When you change pixel dimensions, every output pixel has to be reconstructed from multiple input pixels. The reconstruction algorithm dictates how sharp or how soft the result looks. Nearest neighbor picks the closest source pixel — fast, but produces jagged edges. Use it for pixel art and never for photos.
Bilinear averages 4 surrounding pixels — smooth but a bit soft. Bicubic uses 16 pixels with a cubic weighting — the default for most image editors and the right choice for general photo work. Lanczos (sinc-based) uses 36–64 pixels and produces the sharpest results, especially for large downscales, at a small CPU cost.
ConverterUp uses bicubic by default and switches to Lanczos for downscales above 2×, where the extra sharpness is most visible. After downscaling a photo by more than 4×, applying a mild unsharp mask in your editor restores the perceived sharpness that is naturally lost in any resampling step.
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Frequently asked questions
How does aspect ratio lock work?
When the lock icon is active, changing width updates height proportionally and vice versa, preserving the original aspect ratio. Disable it when you intentionally want to stretch or squash the image to non-proportional dimensions.
What is the maximum image size I can resize?
Up to 50 MB per file. Very high-resolution images (above 8000 pixels on either side) may be slow on low-end mobile devices because resampling runs on the CPU.
Will my image lose quality when resized?
Downscaling is lossy by nature, but ConverterUp uses high-quality bicubic resampling to keep the result sharp. Upscaling cannot add detail that isn't there, so increase dimensions only when strictly needed.
Which formats are supported?
Input and output formats include PNG, JPG/JPEG, WebP, and AVIF. The output format defaults to the input format but can be changed to convert and resize in a single step.
Can I resize by percentage instead of pixels?
Yes. Switch the input mode to percent and enter a value like <code>50</code> to halve both dimensions, or <code>200</code> to double them. The percentage mode keeps aspect ratio locked automatically since both dimensions scale by the same factor.
Why does my upscaled image look blurry?
Resampling cannot invent detail that was never captured. Bicubic and Lanczos interpolate between existing pixels but cannot recover edges that were never sampled. For genuine upscaling (e.g., 2×) you need an AI super-resolution model; for the resizer, treat upscaling as a last resort and prefer requesting a higher-resolution source.
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