Image Resizer
Resize to exact dimensions or social media presets — instant & private
Drop images here or click to browse (up to 10)
JPEG, PNG, WebP, AVIF up to 50MB each
How It Works
Drop Your Images
Drop up to 10 images at once, paste from clipboard, or click to browse. Krunkit detects each image's dimensions automatically.
Set Dimensions or Pick a Preset
Type in exact pixel dimensions, or choose from built-in Instagram, YouTube, Twitter, and Facebook presets.
Download Resized Images
Resized images keep their original format. Download individually or as a single ZIP.
Common Social Media Image Sizes
Instagram Square
1080×1080px. The standard square post format. Works for both feed posts and is safe for most content types.
Instagram Portrait
1080×1350px (4:5 ratio). Takes up more vertical screen space in the feed. Recommended for maximum reach.
YouTube Thumbnail
1280×720px (16:9 ratio). High-resolution thumbnail required for HD videos. Minimum 640px wide.
Twitter / X Post
1200×675px (16:9 ratio). Optimal for in-timeline preview. Supports up to 4 images per tweet.
Facebook Cover Photo
820×312px on desktop, 640×360px on mobile. Use 820×360px as a safe size that works well on both.
LinkedIn Banner
1584×396px for personal profile. Company page cover is 1128×191px. Always test on mobile after upload.
Understanding Image Resizing
Pixels, Resolution, and Display Size
An image's dimensions are measured in pixels — the individual colored dots that make up the picture. A 1080x1080 image contains 1,166,400 pixels. Resolution (DPI/PPI) determines how those pixels map to physical size: 72 PPI is standard for screens, 300 PPI is standard for print. When you resize an image for social media, only pixel dimensions matter because screens display pixels directly. For print, both pixel count and DPI matter — a 3000x2000 image at 300 DPI prints at 10x6.67 inches.
Downscaling vs. Upscaling
Downscaling (reducing dimensions) generally produces excellent results because the algorithm combines multiple source pixels into fewer output pixels, effectively averaging fine detail. This often makes images appear slightly sharper. Upscaling (increasing dimensions) is fundamentally different — the algorithm must invent pixel data that doesn't exist. Traditional interpolation methods like bilinear and bicubic produce smooth but blurry results. AI-based upscalers can generate plausible detail, but this is synthetic data. As a rule, always start with the largest available source image and scale down.
Aspect Ratio and Cropping Behavior
Aspect ratio is the proportional relationship between width and height. A 1080x1080 image is 1:1 (square), a 1920x1080 image is 16:9 (widescreen). When resizing to a target dimension with a different aspect ratio, you must either crop (remove parts of the image), letterbox (add padding), or stretch (distort proportions). Social media platforms each have preferred aspect ratios — Instagram feed favors 1:1 and 4:5, YouTube requires 16:9, Pinterest works best with 2:3. Matching the platform's expected ratio prevents unwanted automatic cropping.
File Size Impact of Resizing
Resizing directly affects file size because it changes the number of pixels that need to be stored. Halving both dimensions reduces pixel count by 75%, which typically results in 50-75% smaller files for lossy formats and even larger reductions for PNG. A 4000x3000 JPEG photo (12 megapixels) might be 4MB, but resized to 1200x900 (1 megapixel) it could be under 200KB — more than enough for web display. Many websites serve images at their original camera resolution, wasting bandwidth on pixels the browser will never display.
Frequently Asked Questions
Does resizing reduce image quality?
Downscaling (making an image smaller) generally looks excellent and can slightly sharpen the image. Upscaling (making an image larger) will degrade quality because new pixel data has to be interpolated. Krunkit warns you when you're upscaling.
Does resizing change the file format?
No. Krunkit keeps your original format (JPEG stays JPEG, PNG stays PNG). Use the Convert tool if you also need to change the format.
What does 'Lock Aspect Ratio' mean?
When locked, changing width automatically updates height (and vice versa) to keep the original proportions. Unlock it to set completely custom dimensions — useful for crop-specific social media presets.
What's the maximum resolution I can resize to?
Up to 16,384×16,384px. In practice, very large output images may take a moment to process since resizing happens on the main thread via Canvas.
Can I batch resize multiple images?
Yes! Drop up to 10 images at once, or paste from your clipboard. All files are resized using the same dimensions or preset. Download individually or as a single ZIP.