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Use this result
Share the current inputs or ask ChatGPT to explain the calculation in context.
What does this calculator estimate?
A 1200x800 image resized to width 600 with aspect preserved becomes 600x400. The inside fit keeps the aspect ratio within the target bounds; exact stretches; cover fills and crops.
- Aspect-ratio-preserving resize scales both dimensions by the same factor (Wikipedia).
- Cover fit fills the target bounds and crops the overflow.
- Resizing down reduces file size roughly in proportion to pixel count.
How resizing works
Resizing recalculates the pixel grid of an image — scaling up interpolates new pixels, scaling down averages them. The fit mode decides how the target dimensions are applied: exact stretches, inside keeps the aspect ratio within the box, cover fills the box and crops.
Limitations to watch for
Upscaling can't create detail that wasn't captured — enlarging a small image softens it. Downscaling loses data permanently (keep the original). The tool uses browser canvas rendering, which is good but not equivalent to professional resampling.
How to use it in practice
For web images, use 'inside' with a max width (e.g., 1200px) to preserve aspect. Use 'exact' when a layout demands a fixed size. Check the output dimensions before downloading.
['Upload an image.', 'Set the target width and height.', 'Choose the fit and download.']
How this calculator works
Formula
Rescales an image to target dimensions with a chosen fit: exact (stretch to W×H), inside (fit within bounds, preserving aspect ratio), or cover (fill bounds, cropping excess).
Worked example
A 1200×800 image resized to width 600 with aspect preserved becomes 600×400.
Assumptions to verify
- The browser canvas API is available.
- The selected fit matches the intended use.
- The original image file is preserved by the user.
Frequently asked questions
How do I resize an image?
Upload it, enter the target width and height, choose the fit, and download — the tool processes it locally in your browser.
What do the fit modes do?
Exact stretches to the dimensions; inside fits within them while keeping the aspect ratio; cover fills them and crops the excess.
Is my image uploaded?
No — everything happens in your browser. Your picture never leaves your device.
Will enlarging make it blurry?
Upscaling interpolates pixels but can't invent detail — small images get soft when enlarged. Start with the highest-resolution original.
What size should I use for the web?
1200px wide is a good max for most layouts; keep file size under ~200 KB with JPEG quality settings.
Does resizing reduce quality?
Downscaling loses detail permanently. Always keep the original file.
Can I resize to a specific file size?
No — the tool controls dimensions, not compression. File size follows from resolution and format.
Cite this tool
BoringToolsKit. “Image Resizer.” boringtoolskit.com/image-resize/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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