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Compress an image to 400 KB
To get an image under 400 KB, PixelFit aims at 400,000 bytes or less, so forms counting 1 KB as 1000 or 1024 bytes both accept it. Estimated from our measured encodes, that is about 1,429 × 1,071 pixels for a 4:3 photo at quality 75, or 1,988 × 2,482 for a portrait.
Under 400 KB
JPG · under 400 KB (at most 400,000 bytes) · original pixel size · white background
PixelFit aims at 400,000 bytes or less, so the file passes whether the form counts 1 KB as 1,000 or 1,024 bytes.
Fit, background and padding white background
Saving presets is part of Pro.
The result appears here: the exact byte count, pixel size and quality, the size before and after, a preview and a download button.
The batch kit (one ZIP for up to 500 photos, several photos merged into one PDF) is part of Pro.
What 400 KB means in bytes
400 KB is 409,600 bytes when 1 KB = 1024 bytes (400 × 1024) and 400,000 bytes when a server counts 1 KB = 1000 bytes. The 9,600-byte gap matters only near the limit. PixelFit aims at 400,000 bytes or less and prints the exact byte count, so you can compare it with the form.
400 KB is 0.39 MB; 25 such files fit in 10 MB. Uncompressed, the 1,429 × 1,071 photo that fits here would need 4.38 MB of raw pixels, so JPEG at quality 75 packs it about 11 to 1.
Largest pixel size that fits 400 KB
The biggest image of each kind, in its own aspect ratio, that stays at or below 400,000 bytes.
| Image | JPG q60 | JPG q75 | JPG q90 | WebP q75 |
|---|---|---|---|---|
| Head-and-shoulders portrait | 2,421 × 3,023* | 1,988 × 2,482 | 1,392 × 1,738 | 3,066 × 3,829* |
| Outdoor landscape (12 MP phone photo) | 1,651 × 1,238 | 1,429 × 1,071 | 1,126 × 844 | 1,527 × 1,145 |
| Scanned typed document page | 2,131 × 2,677 | 1,739 × 2,185 | 1,213 × 1,524 | 2,742 × 3,445* |
| Handwritten letter with signature | 3,498 × 2,875* | 2,800 × 2,301 | 1,884 × 1,548 | 4,461 × 3,667* |
| Flat-colour graphic (flag) | 8,303 × 5,812* | 7,659 × 5,361* | 6,229 × 4,360* | over 9,561 × 6,692 |
A 12 MP phone photo at 400 KB
Our 12 MP landscape sample (4032 × 3024) is about 4.15 MB at quality 90, 11 times the 400 KB budget; even quality 30 leaves 1.26 MB (extrapolated from encodes up to 3,000 px). So the pixels must go down too.
At about quality 75 it fits 400 KB near 1,429 × 1,071 (1.5 MP, 13 % of the original pixels). Quality 60 allows 1,651 × 1,238; quality 90 needs 1,126 × 844.
JPEG quality for fixed pixel sizes under 400 KB
When a form fixes the pixels, only quality can move. Highest quality (of 100) that keeps each size at or under 400,000 bytes:
| Pixel size | Measured on | JPG | WebP |
|---|---|---|---|
| 1080 × 1080 (square social post) | landscape photo | quality 84 (384 KB) | quality 86 (378 KB) |
| 1200 × 1600 (3:4 portrait upload) | portrait photo | quality 92 (374 KB) | quality 94 (344 KB) |
| 1920 × 1080 (Full HD frame) | landscape photo | quality 59 (390 KB) | quality 59 (390 KB) |
| 1240 × 1754 (A4 page at 150 DPI) | scanned typed page | quality 87 (385 KB) | quality 93 (383 KB) |
| 2480 × 3508 (A4 page at 300 DPI) | scanned typed page | quality 39 (385 KB) | quality 76 (387 KB) |
| 3000 × 4000 (12 MP portrait frame) | portrait photo | quality 38 (388 KB) | quality 74 (389 KB) |
Measured JPEG files either side of 400 KB
Real encodes from our test set at quality 75: the largest file that stays under 400,000 bytes and the smallest that goes over.
| Image | Largest under 400 KB | Smallest over 400 KB |
|---|---|---|
| Head-and-shoulders portrait | 1922 × 2400: 374,872 B | 2402 × 3000: 571,851 B |
| Outdoor landscape (12 MP phone photo) | 1200 × 900: 284,926 B | 1600 × 1200: 498,311 B |
| Scanned typed document page | 1592 × 2000: 346,869 B | 1910 × 2400: 465,268 B |
| Handwritten letter with signature | 2400 × 1973: 298,321 B | 3000 × 2466: 455,963 B |
| Flat-colour graphic (flag) | 3000 × 2100: 115,604 B | none: every measured size fits |
JPG, WebP or PNG at 400 KB
At quality 75, WebP holds 1,527 × 1,145 of the landscape photo in 400 KB, JPG 1,429 × 1,071: 14 % more pixels. Portrait gain: 138 % (extrapolated). Typed page gain: 149 % (extrapolated). A moderate gain for the landscape photo at 400 KB, a large one for portraits and typed pages: where WebP is accepted, use it for those. Many portals accept only JPG/JPEG, so this page starts in JPG.
A full-colour PNG is lossless, so its size follows the content. In 400 KB it holds a flat graphic of 6,651 × 4,655 (extrapolated) pixels but a photo of only 518 × 388, against 1,429 × 1,071 as a quality-75 JPG. Reducing a PNG to a palette of up to 256 colours (PixelFit does this when a PNG must shrink) helps graphics far more than photos.
Which uploads fit comfortably in 400 KB
3 of the 6 sizes above keep quality 75 or better under 400 KB (1080 × 1080, 1200 × 1600, 1240 × 1754). At 1,429 × 1,071, quality 90 costs 60 % more bytes than quality 75.
A typed page reaches 2,131 × 2,677 at quality 60 in 400 KB, about 229 DPI if it is an A4 sheet.
How to compress an image to 400 KB
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Open the tool above
It is preset to 400 KB (400,000 bytes or less), JPG output.
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Add your image
Drop, paste or pick it; a PNG, WebP or (where the browser opens it) HEIC file becomes a JPG under 400 KB.
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Pixel size: only if asked
On auto, a typical photo stops near 1,429 × 1,071 at about quality 75.
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Download and check
name-400kb.jpg comes with its byte count, pixels and quality.
Forms that ask for 400 KB
Upload specs in our dataset with exactly 400 KB. Verify with the official notice before you submit.
400 KB limits
Sources
- Measured by PixelFit with sharp 0.35.5 / libvips 8.18.7 on 31 October 2026.
- Sample images, Wikimedia Commons, checked 31 October 2026: landscape (CC0 1.0) commons.wikimedia.org/w/index.php?curid=154070378; portrait commons.wikimedia.org/w/index.php?curid=23956389; typed page commons.wikimedia.org/w/index.php?curid=194775753; handwritten letter commons.wikimedia.org/w/index.php?curid=90423615; flag commons.wikimedia.org/w/index.php?curid=361734 (public domain).
- Binary prefixes, NIST, checked 31 October 2026: physics.nist.gov/cuu/Units/binary.html
Frequently asked questions
How do I compress an image to 400 KB?
Drop it into the tool here, preset to 400 KB. It searches JPEG quality (at most 8 encodes per pixel size), then scales pixels down if needed, until the file is 400,000 bytes or less. A 4:3 photo typically lands near 1,429 × 1,071 at about quality 75.
How do I compress an image to less than 400 KB without losing quality?
Give up pixels before quality: at quality 75, 400 KB holds 1,429 × 1,071 of a photo and 1,988 × 2,482 of a portrait; quality 90 at 1,429 × 1,071 costs 60 % more bytes.
Is 400 KB 400,000 or 409,600 bytes?
Both readings exist: 409,600 bytes (1 KB = 1024) or 400,000 bytes (1 KB = 1000). 400,000 bytes or less passes both.
Can I compress a PNG to 400 KB?
Yes, but a full-colour PNG photo stays big: about 518 × 388 pixels in 400 KB, versus 6,651 × 4,655 (extrapolated) for a flat graphic. As a JPG the photo reaches 1,429 × 1,071.
What pixel size fits 400 KB?
At quality 75: a photo 1,429 × 1,071, a portrait 1,988 × 2,482, a typed page 1,739 × 2,185.
Related
Nearby file sizes
- Compress to 350 KB photo ≈ 1,334 × 1,000
- Compress to 300 KB photo ≈ 1,232 × 924
- Compress to 250 KB photo ≈ 1,128 × 846
- Compress to 500 KB photo ≈ 1,603 × 1,202
- Compress to 512 KB photo ≈ 1,623 × 1,217
- Compress to 600 KB photo ≈ 1,763 × 1,322
More ways to hit 400 KB
- JPG to PDF under 400 KB One image as a PDF
- Image resizer with KB target Any size, pixels and format
Pixel sizes that fit 400 KB
- 1500×1000 landscape about 383 KB as a quality-75 JPG
- 1000×1500 portrait about 383 KB as a quality-75 JPG
- 1080×1350 portrait about 372 KB as a quality-75 JPG
- 1600×900 (HD+) about 368 KB as a quality-75 JPG