Image Resizer
Enter a new width and height for your image. Maintain aspect ratio lock to avoid distortion. See real-time preview and download the resized image.
Image Resizer
Resize images instantly in your browser
Click or drag image here
Resized image dimensions = input dimensions × (new width ÷ original width) for width-proportional, or input dimensions × (new height ÷ original height) for height-proportional. Aspect ratio lock maintains original proportions.
How Image Resizing Works
Image resizing is performed client-side using the HTML5 Canvas API:
1. The selected image file is read via FileReader as a data URL or Blob 2. The image is drawn onto a canvas element at the specified dimensions 3. The canvas toDataURL() method exports the resized image as a JPG or PNG data URL 4. The resulting image is downloaded as a file
**Aspect ratio math**: When 'maintain aspect ratio' is checked: - If only width is entered: new_height = (original_height × new_width) ÷ original_width - If only height is entered: new_width = (original_width × new_height) ÷ original_height - If both are entered without lock: dimensions are used as-is (may distort)
**Quality settings**: The calculator uses 90% JPEG quality by default for a balance between file size and visual fidelity. PNG output preserves exact pixel data (lossless).
- 100% private - images never uploaded to server
- Real-time canvas preview
- Aspect ratio preservation
- JPG or PNG output format choice
Worked Example
Example: Resizing a 3000×2000 pixel photo to fit a 800-pixel-wide web banner:
- Original: 3000 × 2000 pixels - Target width: 800 pixels - With aspect ratio lock checked: new_height = (2000 × 800) ÷ 3000 = 533.33 → rounded to 533 pixels - Result: 800 × 533 pixels (same proportions, no distortion)
Without aspect ratio lock: - Entering 800 × 600 would stretch the image to 800 × 600 (33% taller than proportional), distorting the image.
This is why the 'maintain aspect ratio' option is the default and recommended setting.
Image Format & Quality
- **JPG**: Best for photographs and complex images. Default 90% quality. Smaller file size, slight generational loss. - **PNG**: Best for graphics, logos, images with text or transparency. Lossless compression, larger file than JPG equivalent. - **Resizing down** (e.g., 3000×2000 → 800×533) always reduces file size. Resizing up (e.g., 800×533 → 3000×2000) may make the image appear softer/pixelated. - Recommended maximum upscale: 120% of original size for acceptable quality.
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Open calculator →Frequently Asked Questions
Will resizing an image reduce its file size?
Yes. Resizing an image to smaller dimensions always reduces the file size, since there are fewer pixels to describe. The extent of reduction depends on the original size vs. the new size.
Can I enlarge a small image without it looking pixelated?
Up to about 120% of the original size with reasonable quality. Beyond that, the image may appear soft or pixelated. For significant enlargements, specialized AI upscaling tools are recommended.
Does maintaining aspect ratio change the file dimensions I enter?
No. If 'maintain aspect ratio' is checked, entering one dimension (width or height) automatically calculates the other to preserve proportions. Entering both dimensions without the lock checked uses them as-is, which may distort the image.
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