Resize image to 40KB

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40 KB is a hard limit for many upload fields. This preset aims at 40960 bytes or less and keeps as much detail as that budget allows.

A typical photo fits about 0.27 megapixels in this budget, roughly 600 × 450 pixels. That is more than enough for most web pages and forms, but far less than a modern camera produces.

What fits in 40 KB

File size depends on both pixel count and how much detail the picture holds. The estimates below use rules of thumb for photos saved as JPG at web quality (roughly 0.08 to 0.3 bytes per pixel); your own result will vary with the image.

A typical 12-megapixel phone photo is around 3.5 MB, so reaching 40 KB means roughly a 90× reduction. Most of that comes from reducing the pixel count, not only from lowering quality.

How to stay under 40 KB with the best quality

• Start from the original. Compressing a copy that was already compressed stacks artifacts on top of each other.
• Crop first. Removing empty background means the same 40 KB is spent on the part of the picture that matters.
• Use JPG or WebP for photographs. Keep PNG for flat-color graphics; a photographic PNG is usually many times larger than the same picture as a JPG.
• Do not rename the file extension to change format. Choose the output format in the tool so the file is actually re-encoded.
• Expect visible softness on detailed images. If a form lists both a size limit and minimum pixel dimensions, check them against the table above before you start.

About this size limit

Here 1 KB is 1,024 bytes, so 40 KB is 40960 bytes. Some systems count 1 KB as 1,000 bytes, which makes their limit about 2.3% smaller. If a portal is strict, choose a target a little below its stated limit; an extra margin costs very little quality.

How to resize an image to 40KB

1. Add your image. Select a photo or drag it onto the box above. JPG, PNG, WebP, AVIF, HEIC and BMP files are accepted, and the file stays on your device.
2. Check the 40 KB target. The editor opens with the target file size already set to 40 KB and the dimensions left on Auto, so the tool only reduces quality and size as far as it must.
3. Pick an output format. JPG or WebP usually give the smallest result for photos. PNG is lossless, so it cannot be squeezed by lowering quality.
4. Download and verify. Download the result and check its size in your file manager. If it is still above 40 KB, lower the pixel dimensions slightly or crop out unneeded areas and run it again.

Related presets

More in this category: Resize Image to a Target File Size. For several photos at once, use the bulk image resizer.