Estimate how large an image file will be from its dimensions, format and quality — or upload an image to measure the real exported size at different quality levels. Plan your image budget before you export. 100% in your browser — your image never leaves your device.
Estimates use typical compression ratios for each format and image type. Real exports vary with the specific image — use Measure mode for exact sizes.
Drop an image here or click to choose
Re-encoded locally at several quality levels
| Format / Quality | File size | vs original |
|---|
🔒 Everything runs in your browser. Your image is never uploaded, logged or stored.
The Image Size Estimator helps you predict how large an image file will be before you export it. Enter the width, height, format and quality and it estimates the file size using realistic compression ratios, or switch to measure mode and upload an image to see the exact exported size at several quality levels — re-encoded right in your browser. It is the fastest way to plan an image budget and choose the right format and quality for the web.
It is part of the Performance & Code Tools group in our free SEO Toolkit. Use it alongside the Page Size Calculator to budget total weight, the Base64 Image Encoder to inline tiny images, and the Critical CSS Extractor to speed up first paint, and the JavaScript Minifier to trim script weight. For more image work, see our Image Tools. Everything runs in your browser — your image never leaves your device.
Estimate from dimensions, or measure the real thing.
Predict size from width, height, format and quality.
Upload an image and see actual sizes at several quality levels.
See JPEG, WebP, AVIF, PNG and GIF side by side.
Images are processed locally and never uploaded.
Estimate ahead, or measure exactly.
Estimate from dimensions or measure a file.
Dimensions and format, or upload an image.
See the estimated or measured file size.
Pick the format and quality that fit your budget.
A 1200 × 630 web photo at quality 80.
Image size estimation predicts how many bytes an image will occupy once it is saved in a given format at a given quality. Because images are usually the heaviest part of a web page, knowing the likely file size before you export helps you choose the right dimensions, format and compression — and avoid shipping a multi-megabyte photo where a small one would do. This tool both estimates from dimensions and measures real exports in your browser. It is part of the Performance & Code Tools group.
| Format | Best for |
|---|---|
| AVIF | Smallest files for photos; newer, very efficient |
| WebP | Great balance of size and support for photos and graphics |
| JPEG | Photos where wide compatibility matters |
| PNG | Graphics, logos and anything needing transparency |
| GIF | Simple animations and very basic graphics |
Size grows with the pixel count — width times height.
Lower quality means smaller files for lossy formats.
Detailed, textured images compress less than flat ones.
Modern formats like AVIF and WebP pack more into fewer bytes.
Estimate mode uses typical bits-per-pixel ratios for each format and image type, scaled by your chosen quality. It is a realistic ballpark for planning, but every image compresses differently depending on its content. For an exact figure, use measure mode, which re-encodes your actual image and reports the true byte size.
It draws your image onto an HTML canvas and re-exports it at several formats and quality settings using the browser's built-in encoders, then reports the resulting byte sizes. Because this uses the same encoders your browser ships with, the numbers closely reflect what you would get exporting from a real tool.
Measure mode can only produce formats your browser supports for encoding. Most modern browsers support WebP, and many now support AVIF, but if yours does not, that row is skipped rather than shown with a misleading value. JPEG and PNG are supported everywhere.
No. Both modes run entirely in your browser. In measure mode the image is read locally with the FileReader interface and re-encoded on a canvas; nothing is uploaded, logged or stored. The tool is safe for unreleased artwork and confidential client images.
Budget image weight before exporting.
Decide between JPEG, WebP and AVIF.
Find the quality that balances size and looks.
Size variants for different screen widths.
Use the Image Size Estimator with these tools from the SEO Toolkit: budget total weight with the Page Size Calculator, inline small images with the Base64 Image Encoder, speed up first paint with the Critical CSS Extractor, shrink markup with the HTML Minifier, compress stylesheets with the CSS Minifier, and explore more in our Image Tools.
Anyone who puts images on the web.
Everything about estimating image size.
It predicts how large an image file will be from its dimensions, format and quality, and it can also measure the exact exported size of an uploaded image at several quality levels. This helps you plan image weight and pick the best format before publishing.
Yes, completely. There is no cost, no sign-up and no limit on how many images you estimate or measure. The tool runs entirely in your browser, so there are no server costs and nothing to pay for.
No. Both modes run in your browser. In measure mode the image is read locally with the FileReader interface and re-encoded on a canvas, so nothing is uploaded, logged or stored. The tool is safe for unreleased artwork and confidential client images.
Estimate mode uses realistic bits-per-pixel ratios for each format and image type, scaled by quality, so it is a good ballpark for planning. Because every image compresses differently, use measure mode when you need the exact byte size for your specific image.
It draws your image onto a canvas and re-exports it using your browser's built-in encoders at several formats and quality settings, then reports the resulting byte sizes. These reflect what your browser would actually produce, so they are close to real export tools.
For photos, AVIF is usually smallest, followed by WebP, then JPEG. PNG is larger but lossless and supports transparency, making it best for graphics and logos. The right choice balances file size against quality needs and how widely the format is supported.
Measure mode can only output formats your browser can encode. Most browsers support WebP and many support AVIF, but if yours does not, that row is skipped rather than shown with a misleading number. JPEG and PNG work everywhere.
Complexity describes how much detail and texture an image has. Flat graphics with few colours compress to very small files, while richly detailed photos with lots of texture compress less and produce larger files at the same dimensions and quality. The estimator lets you account for this.
Yes, indirectly. Lighter images load faster, which improves user experience and Core Web Vitals, both of which support better rankings. Right-sizing and compressing images is one of the most effective ways to speed up a page, especially on mobile connections.
It is the raw size the image would occupy with no compression, roughly three bytes per pixel. It is a useful reference point that shows just how much compression each format achieves compared with storing every pixel directly.
Yes. The estimator is fully responsive, so you can estimate or measure image sizes from a phone or tablet. Entering dimensions, choosing formats, adjusting quality and uploading an image to measure all work the same as on desktop.
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Predict image file size from dimensions, or measure the real export at different quality levels — free, private and instant in your browser.
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