How to reduce an image to a KB size
- Tap Choose image above (JPG, PNG, WebP, HEIC and more) and pick your photo.
- On the Exact KB tab the target is already 50 KB and the rule is At or under target (most portals). Change either if your form says otherwise.
- Tap Compress to target. The gauge shows each pass. A large phone photo usually takes a few seconds on a computer, longer on an older phone.
- Compare the result with the original. The result line shows its pixel size and file size.
- Tap Download result, and upload that file to your form.
The three size rules
| Rule | Use it when | What you get |
|---|---|---|
| At or under target | The form gives a maximum ("max 50 KB") | The largest file that doesn't go over |
| As close to target as possible | You want about a size, either side is fine | The file nearest the target |
| At least target | The form gives a minimum ("at least 20 KB") | A file of at least that size, picture unchanged |
How it finds the size
File size doesn't follow quality in a straight line, so the tool searches: it tries a quality level, measures the bytes, narrows the range and repeats. If even the lowest sensible quality is too big, it looks for the largest pixel size that fits at good quality, then fills the remaining room with quality. You get the best-looking file that meets the rule, usually within 1–2% of the target. On our test computer that took 1–4 seconds for a 24–26 MP photo; older phones take longer.
What each target gives you
Pixel size the tool chose for five real photos (12–26 megapixel originals):
| Photo | 10 KB | 20 KB | 50 KB | 100 KB | 200 KB |
|---|---|---|---|---|---|
| Portrait, plain wall (26 MP) | 251×376 px | 386×579 px | 676×1013 px | 1040×1559 px | 1581×2372 px |
| Indoor selfie (24 MP) | 202×303 px | 321×481 px | 606×909 px | 997×1496 px | 1584×2377 px |
| Busy street market (24 MP) | 144×216 px | 240×360 px | 373×559 px | 515×773 px | 800×1200 px |
| Group photo outdoors (24 MP) | 216×144 px | 348×232 px | 599×400 px | 868×579 px | 1379×920 px |
| Clear sky, little detail (12 MP) | 846×1127 px | 1208×1610 px | 1860×2480 px | 2490×3320 px | 3024×4032 px |
Test photos: free-to-use Unsplash photos (12–26 megapixels; Unsplash re-encodes its downloads); PixKB Exact KB, "At or under target", desktop Chromium on our test server, October 2026. Pixel sizes are what the tool chose to fit, and can differ slightly between browsers; bytes are exact. Sizes in decimal KB (1 KB = 1,000 bytes).
Jump to a page for the common limits: 10 KB, 20 KB, 50 KB, 100 KB, 200 KB, or increase a file to a minimum. For a specific form, the form presets apply its pixel size and KB rule together.
If the form also sets a pixel size
To fit a small KB limit, the tool makes the picture smaller in pixels when quality alone can't get there. If your form also requires dimensions (for example 600×600 or 350×467), do this instead: use the form's preset if there is one, which handles both rules at once. Otherwise set the size on the Dimensions tab, tap Resize, then Keep editing this result, and compress that to the KB limit. The pixel size stays exactly as you set it.
1,000 or 1,024 bytes?
Forms count a kilobyte either way, and the difference can decide a tight limit: a 50,500-byte file is 50.5 KB to one system and 49.3 KB to another, so it passes one 50 KB limit and fails the next. PixKB aims for the stricter count: a maximum of 50 KB gives at most 50,000 bytes, which passes either way.
Common mistakes
- Typing MB as KB. 1 MB is 1,000 KB. A "2 MB maximum" means you may not need to compress much at all.
- Compressing a compressed copy. Start from the original photo, not a WhatsApp or email copy.
- Not cropping. Background and empty space use up the limit; crop to what matters first.
- Ignoring the minimum. "20–50 KB" means a 15 KB file fails too.
Frequently asked questions
How do I reduce an image to a specific KB size?
Type the size in the target box, choose the rule that matches your form (usually "At or under"), tap Compress to target and download.
How exact is it?
Usually within 1–2% under the target: 49,132 bytes for a 50 KB target in our test. JPEG sizes move in small steps, so it can't always land on the exact byte.
Why does the tool reduce the pixel size?
When the target is far below the photo's size, quality alone would make it blocky. A smaller, clean picture looks better, so the tool picks the largest size that fits at good quality.
Can I keep my exact pixel size?
Yes: resize on the Dimensions tab first, tap Keep editing this result, then compress. Or use a form preset.
What's the difference between KB and pixels?
Pixels are the picture's width and height; KB is the file's size on disk. Forms can limit both. Our pixels to KB guide explains how they relate.
Does it work for PNG files?
Yes. PNG, WebP, HEIC and other formats are accepted; the result is a JPEG, which is what KB-limited forms ask for.
Can I reduce a PDF's size here?
Use the PDF compressor for PDFs; it keeps text sharp and selectable.
Is there a size limit for the original?
Files up to 60 MB can be opened.
Is it really free?
Yes. No signup, no watermark, no limit on how many files.
Is my image uploaded?
No. Everything runs in your browser on your device.