Image Tools
Image Resizer
Change bounded static raster pixel dimensions with an optional aspect-ratio lock.
Enter the values and review the result.
Resize settings
Processing stays in this browser and makes no file-upload or conversion request.
One static JPEG, PNG, or WebP; 1 byte–8 MiB; at most 8192 px per side and 16000000 pixels.
Choose an image and bounded output dimensions.
Original-ratio dimension arithmetic
With a decoded source width W and height H, a new width w derives height as Math.round(w × H ÷ W). A new height h derives width as Math.round(h × W ÷ H). Each result must remain within 8192 pixels per side and 16000000 total pixels.
Example: a 2400 × 1600 source changed to width 1200 derives height Math.round(1200 × 1600 ÷ 2400) = 800.
Rendering and limitations
The output uses high browser canvas smoothing where supported and retains the validated source MIME. It does not claim a professional resampling algorithm or restored detail.
Metadata may not survive, decoded orientation may be normalized, color appearance may differ, and file size can increase or decrease. Processing is local but is not guaranteed privacy, deletion, malware scanning, or archival fidelity.
Quick answers
What this calculator answers
- Purpose: Changes the pixel dimensions of one validated static JPEG, PNG, or WebP image.
- Aspect ratio: The initial lock derives the other side from the original decoded ratio using final whole-pixel rounding.
- Boundary: Upscaling is bounded but cannot restore missing source detail; unlocked dimensions can distort the image.
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
File and image results can vary by file structure, browser support, size, fonts, compression, and format limits. Review downloaded files before using or sharing them, and avoid sensitive files unless you understand how the tool handles them.
Reference check
Sources and references
These references provide background context for the topic. They do not replace official advice or documents for personal decisions.
- File API
World Wide Web Consortium
- Canvas toBlob
WHATWG
- ImageBitmap and image decoding
WHATWG
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Choose one static JPEG, PNG, or WebP image.
Keep aspect lock on for proportional resizing, or turn it off and enter both dimensions.
Choose Resize Image, review the preview, then download or Reset.
Related Tools
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Base64 to Image
Strictly decode canonical Base64 into a validated static JPEG, PNG, or WebP image.
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Create one PDF from ordered JPEG images with automatic page sizing.
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Convert every PDF page to a JPG image and download the ordered pages as a ZIP.
Related Guides
Background reading and explanations related to Image Resizer.
Frequently Asked Questions
Common questions about Image Resizer and how to read the result.
How does aspect lock work?
Width changes derive height, and height changes derive width, from the original decoded ratio. The final derived side uses Math.round once.
Can I enlarge an image?
Yes, within the dimension and pixel caps. Upscaling does not create additional source detail and may look softer.
Which formats are retained?
JPEG stays JPEG, PNG stays PNG, and WebP stays WebP. Encoder substitution is rejected.
Are SVG or animated images supported?
No. SVG, GIF, animated PNG, animated WebP, and other unsupported formats are rejected before resizing.
What can change besides dimensions?
Canvas re-encoding may affect metadata, decoded orientation, file size, color/profile behavior, transparency behavior, and visual quality.