Base64 Image Size Calculator
Calculate the size a file becomes when encoded as Base64, which adds about 33 percent overhead, to plan data URIs and inline images.
Last reviewed by the Radiatus Cloud team
Calculate how much larger a file becomes when encoded as Base64.
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Calculate Base64 encoding size
Base64 encoding represents binary data as text, which is how images are embedded directly in HTML or CSS as data URIs. The trade-off is size: Base64 encodes every three bytes as four characters, so the encoded data is about one third larger than the original. This calculator computes the Base64 size from your file size, showing the exact byte count and the percentage overhead. A fifty-kilobyte image becomes roughly sixty-eight kilobytes when Base64-encoded.
The overhead is close to thirty-three percent, plus a little padding, regardless of the file type.
When to inline images
Embedding small images as Base64 data URIs avoids a separate network request, which can speed up loading for tiny icons and graphics. However, because of the thirty-three percent size increase and the fact that inlined images cannot be cached separately, it is usually only worthwhile for very small images. Knowing the encoded size helps you decide whether inlining an image is a net benefit.
For larger images, a normal linked file is almost always smaller and more cacheable than a Base64 data URI. All calculation happens locally in your browser.
Notes
This Base64 Image Size Calculator tool runs entirely in your browser, so nothing you enter is uploaded or stored on a server. The generated output is plain, standards-compliant code that you can copy, paste, edit and reuse freely in your own projects, documents and designs without any attribution or sign-up.
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Frequently Asked Questions
How much bigger is Base64?
About thirty-three percent larger, because every three bytes of data become four Base64 characters, plus a small amount of padding.
Why embed images as Base64?
To avoid a separate network request, which can help for very small images like icons, at the cost of a larger size and no separate caching.
When should I not inline an image?
For larger images, since the size increase and loss of separate caching usually outweigh the saved request. A linked file is better.
Is the overhead always the same?
It is close to thirty-three percent for any file, with slight variation from padding, since the encoding ratio of three bytes to four characters is fixed.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter the original file size in kilobytes.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
Related Tools
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ImageExtract hidden EXIF data (Camera, GPS, Settings) from images.
Favicon Generator
ImageGenerate favicons and app icons at every required size from one source image, with the exact HTML to reference them.
Placeholder Image Generator
ImageGenerate placeholder images at any size with custom colours and label text. Produced in your browser as downloadable files, no external hotlinking.