Image Compression Estimator
Estimate the file size of an image at JPG quality 60, 75, 85 and 95, plus WebP, to plan page weight and CDN transfer.
Image details
Estimated file sizes
JPG at quality 85
Estimates use typical bits per pixel. Real files vary with detail and noise.
Quality 75 to 85 is the sweet spot
Most people cannot tell JPG quality 85 from quality 95, yet the file at 95 is often close to twice the size. For images that are not the hero of the page, quality 75 or even 60 usually looks fine. Compressing sensibly saves bandwidth, helps Core Web Vitals such as Largest Contentful Paint, and lowers CDN costs at scale.
How the estimate works
The calculator multiplies the pixel count by a typical number of bits per pixel for each quality level and content type. Photos carry the most detail, while flat graphics and screenshots compress further. Treat the numbers as a planning guide: a noisy photo can be larger and a simple one smaller.
- Resize to the largest size the image is actually displayed at before you compress.
- Use WebP or AVIF where you can, with JPG as a fallback.
- Lazy-load images below the fold so they do not compete with the main content.
Frequently asked questions
What about WebP?
WebP files are typically 25 to 35% smaller than JPG at similar visual quality, and all modern browsers support it. Serve WebP first with a JPG fallback if you still support very old browsers.
Should screenshots be JPG or PNG?
Screenshots with text and flat color often look sharper as PNG or lossless WebP. If a screenshot contains photos or gradients, a high-quality JPG or lossy WebP is usually much smaller.