Compress an Image to an Exact File Size

How it works

Choose your images, pick a target file size and press Shrink. This is the compression question asked backwards: you do not set a quality and accept whatever size comes out, you set the size and the highest quality that fits underneath it is found for you. The tool encodes the picture at high quality, measures the result, and if it sits above the limit it lowers the quality and measures again — halving the search range each round, so it settles in at most eight tries. A result line reads, for instance, "3.2 MB → 96 KB (target 100 KB) · quality 58%" — the file landed under the limit, and pulling the quality down to 58 was all it took. When quality alone is not enough, the second setting takes over: with "Shrink if needed" selected the pixel dimensions come down as well. If the target still cannot be met, the result line says so plainly instead of handing you the wrong size in silence.

This tool is also known as compress image to 200kb, reduce image size to 100kb, compress photo to exact size, shrink image file size, reduce image size by percentage.

What is Kilobyte and megabyte (KB, MB)?

Kilobyte and megabyte are the units file size is measured in: 1 MB is 1024 KB, and 1 KB is 1024 bytes. Upload forms almost always state their limit in KB ("200 KB maximum") while your phone shows the same file in MB, so realising that 0.2 MB and 200 KB are the same thing clears up most of the confusion. One more wrinkle: some systems count 1 MB as 1000 KB rather than 1024, which is why files sitting exactly on the line are sometimes rejected. Landing a little under the limit is the safe move.

What is JPEG quality value?

The JPEG quality value is a setting from 0 to 100, and it does not mean "how much of the picture is kept" — it decides how much detail gets thrown away. The relationship is not linear: dropping from 95 to 85 can halve the file with nothing visible happening, while every step below 50 leaves block edges and colour smearing behind. The same quality value also produces very different file sizes on different pictures, because flat areas like sky are cheap to store and detailed ones like foliage or fabric are expensive. That is why hitting a target size is a matter of measuring rather than calculating.

What is Binary search?

Binary search finds a value by eliminating half of the remaining possibilities with every attempt. What is being searched for here is the highest quality that still fits under the target size: the top quality is tried first, then the bottom one, and after that each round measures the middle of the remaining range and moves the lower or the upper bound to that point depending on the result. Because the range halves every round, eight attempts give the same precision as testing hundreds of quality values one by one. Limiting the number of rounds matters: every attempt re-encodes the whole photograph, and an unbounded search would freeze the browser.

What is the difference between compressing and shrinking to a target size?

Both make the file smaller, but they ask the question from opposite ends. In a compression tool you choose the quality and accept whatever size falls out: you picked 75, the file came out at 340 KB, and if it has to be under 200 KB you go back and try again. Here you state the size and the quality is searched for you: you said 200 KB, and the highest quality that fits underneath is found by measuring. If your test is "does the photo still look good", the compression tool is the right place; if it is "will this form accept it", you are already there. Official uploads do not negotiate over their limits, which is why the second question comes up far more often.

Which limit for which job?

Usually the limit is not yours to choose — the system you are uploading to sets it. Use whatever number the form states; when it states nothing, the habits below are a sensible starting point.

Do not aim far below the limit. Uploading a 60 KB file to a form that allows 200 KB is accepted but throws away quality for nothing; sitting just under the limit gives the best-looking result.

• ID and passport photos → 100-200 KB
• Application form attachments, scanned documents → 200-500 KB
• Photo on a CV → 500 KB
• Email attachment, several images at once → 1 MB
• Anything going to print → 2 MB, or do not compress at all

The target is not always reachable — and that has to be said

Quality has a floor. This tool will not go below 30, because a photograph falls apart into blocks down there and stops being usable. On a very large image, a tight target like 100 KB may simply be out of reach for quality alone.

When that happens the result line reads "target 100 KB not reached" and shows the size actually achieved. Pretending the target was met and handing you a 128 KB file labelled 100 KB would leave you stranded on the upload screen.

The way out is in the pixel dimensions: a 4000-pixel-wide photograph does not need to be 4000 pixels wide for a form. Select "Shrink if needed" and the dimensions come down too, which makes the target reachable in almost every case — the new pixel size is printed on the result line.

Why is the output always JPG?

Landing on a requested file size needs an adjustable quality dial. JPEG has one; PNG does not, because it is lossless and its size can only be cut by changing the picture itself. That is why the output is JPG whatever you feed in.

There is a cost: transparency is lost and transparent areas sit on white. For a logo or a graphic that has to keep its transparency, this is the wrong tool.

Frequently asked questions

How do I get a photo under 200 KB?

Choose the image, set the target file size to 200 KB and press Shrink. The highest quality that still fits under 200 KB is found for you, and the result line shows both the new size and the quality used.

What if the target cannot be reached?

The result line says so: it reads "target 100 KB not reached" and shows the size actually achieved. Quality is never pushed below 30, because the photograph becomes unusable there. Select "Shrink if needed" and run it again.

Do the pixel dimensions change?

Not by default — only the quality is lowered. If you select "Shrink if needed" and quality alone is not enough, the pixel dimensions come down as well, and the result line reports the new size in pixels.

What happens if the file is already under the target?

It is returned untouched. Re-encoding a file that already fits only burns quality and can even make it larger, and the result line points that out.

Can I shrink several photos at once?

Yes. Select as many files as you like; each one is searched separately, because the same quality value produces wildly different sizes on different pictures.

Does "Shrink if needed" damage the picture?

Lowering the pixel dimensions costs less than pushing the quality to the floor: you get the same picture in a smaller frame with its detail intact. Once the scale drops below half, the tool resamples with a detail-preserving method (Lanczos), so the smaller photo stays crisp and also compresses more easily, which means the target is met at a higher quality. The new pixel size is written in the result line.