Pixel dimensions (width × height) define how many individual dots make up an image. Physical print size depends on both pixel dimensions and DPI (dots per inch). A 1200×1200 px image at 300 DPI prints at 4×4 inches; the same file at 72 DPI would be 16.7×16.7 inches on screen. For web use, only pixel dimensions matter — DPI metadata is irrelevant in browsers.
Free Online Image Resizer
Resize Any Image to Exact Pixels or Percentage
Resize JPG, PNG, and WebP images to any width and height in pixels, or scale by percentage. Aspect ratio lock keeps your images from distorting.
Exact pixel dimensions
Percentage scaling
Aspect ratio lock option
Drop your image here
or browse files
JPG, PNG, WebP, GIF • Up to 100 MB
Quick Presets
px
px
Output: —
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SSL Encrypted
Files deleted in 2h
Fast processing
No signup needed
Simple & Fast
How to Use Image Resizer
Convert your files in three simple steps — no software, no signup.
01
Upload Your Image
Drop or select any JPG, PNG, WebP, or GIF image. Up to 100 MB supported.
02
Set New Dimensions
Enter target width and height in pixels, or a scale percentage. Toggle aspect ratio lock to prevent distortion.
03
Download Resized Image
Your resized image is ready instantly. Original format and quality are preserved.
Features
Why Use Image Resizer?
Pixel-Perfect Sizing
Enter exact pixel dimensions for width and/or height. Perfect for social media specs, print layouts, and UI mockups.
Percentage Scaling
Scale down to 50% or up to 200% of the original size without worrying about exact pixel counts.
Aspect Ratio Lock
Lock the aspect ratio so entering one dimension automatically calculates the other — no stretching.
Preserves Transparency
PNG and WebP files with transparent backgrounds maintain their alpha channel after resizing.
Upscale & Downscale
Make images larger or smaller. Downscaling uses Lanczos resampling for the sharpest results.
Secure & Private
No image is stored beyond 2 hours. Resizing happens server-side in a sandboxed environment.
Compatibility
Supported Formats
All the formats you need, all in one place.
| Format | Description | Extension | Best Used For |
|---|---|---|---|
| JPG | Resized JPEG with quality control | .jpg |
Web photos, email attachments, social posts |
| PNG | Lossless resized PNG with transparency | .png |
UI assets, logos, screenshots |
| WEBP | Resized WebP for optimal web delivery | .webp |
Website images, Next.js Image optimization |
| GIF | Resize static or animated GIFs | .gif |
Animated thumbnails, icon sets |
| BMP | Lossless bitmap resizing | .bmp |
Windows desktop backgrounds, legacy apps |
| TIFF | High-fidelity TIFF resize for print | .tiff |
Print production, archival images |
FAQ
Frequently Asked Questions
Yes — enable the aspect ratio lock. When you enter a width, the height is calculated automatically to maintain the original proportions.
You can resize up to 10,000 × 10,000 pixels. Very large upscaling may reduce sharpness — for AI-powered upscaling with detail enhancement, use our Image Upscaler tool.
Single-file resizing is available for free. Bulk resizing via API or batch mode is available for registered users on the Pro plan.
We use Lanczos resampling for downscaling (sharpest results) and bicubic interpolation for upscaling, giving smooth results without jagged edges.
By default the output is the same format as your input. You can also choose a different output format in the options panel.
Common presets: Instagram post 1080×1080, Twitter header 1500×500, Facebook cover 820×312, LinkedIn banner 1584×396. Enter these exact values in the width and height fields.
Real-World Uses
Who Uses Image Resizer?
From everyday users to professionals — see how people rely on this tool every day.
Social Media Manager
Resize for Social Platforms
Quickly resize photos to exact Instagram, Twitter, Facebook, or LinkedIn dimensions without distortion using the aspect ratio lock.
Web Developer
Generate Responsive Breakpoints
Create 1x, 2x, and 3x versions of the same image for responsive srcset attributes and retina display support.
E-commerce Seller
Standardise Product Thumbnails
Resize product images from varied camera sizes to a uniform 800×800 or 1000×1000 for consistent product listing grids.
Email Marketer
Size Images for Email Templates
Resize images to your email template width (typically 600px) before embedding to prevent broken layouts in Gmail and Outlook.
App Developer
Create App Icon Sizes
Resize a master icon to all required iOS and Android sizes (1024px, 512px, 192px, 144px etc.) in quick succession.
Designer
Resize Mockups for Presentations
Scale mockup images to exact slide dimensions (1920×1080, 1280×720) so they fill your PowerPoint or Keynote perfectly.
Why TransmuteBox?
TransmuteBox vs. Alternatives
See how we compare to desktop software and other online converters.
| Feature |
Our Tool TransmuteBox |
Photoshop | Other Online |
|---|---|---|---|
| Exact pixel dimensions | |||
| Percentage scaling | Varies | ||
| Aspect ratio lock | Varies | ||
| Preserves transparency | Varies | ||
| Lanczos downscaling | |||
| No software install | |||
| Files auto-deleted (2 h) | Varies | ||
| API access | Pro |
Under the Hood
Technical Specifications
Built on industry-standard open-source tools for maximum quality and reliability.
Limits & Restrictions
- Max file size: 100 MB (free)
- Max output resolution: 10,000 × 10,000 px
- Max upscale: 200% (use AI Upscaler for beyond 200%)
Pillow
Lanczos
bicubic
JPEG
PNG
WebP
GIF
Conversion Engine
Pillow 10.x (Lanczos / bicubic resampling)
Output Quality
Lossless for PNG/WebP; JPEG quality 90 default (adjustable)
Average Speed
Resizing completes in under 2 seconds for most images
Data Security
HTTPS transfer · isolated temp dir · auto-purged in 2 h
Downscale algo
Lanczos (sharpest)
Upscale algo
Bicubic interpolation
Ratio lock
One dimension auto-calculates
Complete Guide
Image Resizing Guide: Pixels, Aspect Ratios & Social Media Sizes
Resizing images correctly is a fundamental skill for web developers, designers, and content creators alike. Getting dimensions wrong can break layouts, slow pages, or produce blurry visuals. This guide covers everything from resampling algorithms to social media presets.
Understanding Pixel Dimensions vs Physical Size
Lanczos vs Bicubic: Which Resampling Is Best?
Lanczos resampling samples a wider neighbourhood of pixels and applies a sinc-based filter, preserving edge sharpness better than bicubic when reducing image size. It is the gold standard for downscaling photographs. Bicubic uses a 4×4 pixel grid and is faster — suitable for upscaling where you want smooth results. Nearest-neighbour (not used here) simply duplicates pixels and is only suitable for pixel art.
Aspect Ratio Lock and Why It Matters
An aspect ratio is the proportional relationship between width and height (e.g. 16:9, 4:3, 1:1). Resizing without locking the ratio stretches or squishes the image. The aspect ratio lock calculates the missing dimension automatically: if your original is 1600×900 and you enter a width of 800, the height becomes 450 — maintaining the 16:9 ratio perfectly.
Social Media Image Size Cheatsheet
Quick reference for common platforms: Instagram — feed post 1080×1080 (square), story 1080×1920, landscape 1080×566. Twitter/X — post image 1200×675, header 1500×500, profile 400×400. Facebook — cover 820×312, shared image 1200×630. LinkedIn — post image 1200×627, banner 1584×396. YouTube — thumbnail 1280×720.
When to Use Percentage Scaling Instead of Fixed Pixels
Percentage scaling is useful when you want to reduce all images by the same relative amount without knowing exact output dimensions. Scale to 50% for quick thumbnail generation, or 75% to cut file size while preserving proportions. It is particularly handy for batch operations where every input image has different dimensions but you want each output halved.