How to compress a photo or signature to 20 KB

Why 20 KB is harder than it sounds

20 KB is 20,000 bytes, or 160,000 bits. A 12-megapixel phone photo has 12 million pixels, so at full size each pixel would get about one hundredth of a bit, far too little for a usable picture. The only way to fit is to use fewer pixels: crop away everything you don't need, and scale the rest down to a few hundred pixels across.

That's fine for upload forms: they usually display your photo small, often at around 200 pixels wide. A sharp small photo looks much better than a large one crushed into blocks.

A photo to 20 KB, step by step

1. Start with a good photo: plain light background, daylight on your face, sharp focus. Noise from a dark room uses up bytes fast.
2. Crop to head and shoulders with Crop Image. If the form names a size such as 200 × 230 pixels, set it with Resize Image.
3. Open Compress to Exact Size and choose 20 KB.
4. Check the preview, the new dimensions and the final size, then download.

The tool searches for the highest JPEG quality that fits. If the photo is still too big, it scales it down while keeping its shape, and it never goes over your limit.

A signature to 20 KB

Signatures are easy to fit, because they are mostly white paper:

1. Sign on plain white paper with a dark blue or black pen, a little larger than usual.
2. Photograph it in daylight, straight from above, without your shadow on the page.
3. Crop tightly around the signature, leaving a small white margin.
4. If the form gives dimensions (often something like 140 × 60 or 300 × 80 pixels), resize to them.
5. Compress to 20 KB, or to 10 KB if that's the limit. A clean signature usually fits easily.

Need the photo and signature in one image? The Photo and Signature tool puts them together and then you can compress the result.

What fits in 20 KB

A rough guide for a good-looking JPEG (results depend on the detail in the picture):

These are estimates. The tool works out the right balance for each image automatically.

When the form says "between 10 KB and 20 KB"

Many portals set a minimum as well as a maximum, and reject files that are too small. Choose a target just under the maximum (for example 19 KB) rather than the smallest possible file. The tool aims as close to your target as it can without going over, so the result lands inside the range.

The same applies to dimensions: a file can be the right size in KB and still be refused for the wrong width or height.

Checking the size: 20 KB or 19.5 KB?

"KB" can mean 1,000 or 1,024 bytes (NIST calls the 1,024-byte unit a kibibyte). Picsawa counts 1 KB as 1,000 bytes, the stricter reading, so a "20 KB" result is accepted by sites that count either way. Windows counts in 1,024s, so it shows a 20,000-byte file as 19.5 KB; that's the same file.

Common mistakes

• Compressing a WhatsApp copy. It has already lost detail; start from the original photo.
• Compressing again and again. Each round adds blur. Go back to the original and compress once to the final target.
• Renaming .png or .heic to .jpg doesn't convert the file. Let the compressor convert it, or use HEIC to JPG.
• Keeping the whole scene. Cropping to what matters is the single biggest saving.

For a bit more room, see how to compress a photo to 50 KB.