The short answer
Open the image compressor, choose “To a file size”, type 100 and download the result. It lowers the JPG quality just enough to fit and only shrinks the picture if quality alone isn't enough. If you'd rather do it by hand: resize the photo to about 1,000–1,200 pixels wide, then save it as JPG at 70–80% quality.
Job portals, exam registrations, visa forms and government websites love a hard limit: “Photo must be under 100 KB.” Your phone, meanwhile, produces photos of 2–5 MB — twenty to fifty times too big. The good news is that a 100 KB photo can still look perfectly sharp on screen. The trick is knowing which two settings actually control file size, and which popular “fixes” do nothing.
On this page
The only two things that really change file size
A JPG's size comes down to:
- How many pixels it has. A 12-megapixel phone photo (about 4000 × 3000) holds 12 million pixels. Halve the width and height and you're down to 3 million — a quarter of the data.
- The compression quality. Dropping from 95% to 75% often cuts the size by more than half with no difference you can see at normal viewing size.
Everything else is a minor factor. Busy, detailed scenes (grass, gravel, a patterned shirt) compress worse than a plain background, so two photos at the same settings can differ a lot — which is why a fixed recipe sometimes misses the target.
Changing DPI does nothing
A very common suggestion is to “change the image to 72 DPI”. DPI is just a printing instruction stored in the file; it doesn't change the number of pixels, so the file size stays the same. Change the pixel dimensions instead.The fastest way: compress to a target size
- 1Open the image compressor and drop in your photo.
- 2Switch to To a file size and tap 100 KB (or type your limit).
- 3Check the preview. The tool shows the quality and dimensions it used to fit.
- 4Download. The file is always under your limit — if a photo truly can't get that small, the tool tells you instead.
It tries the highest quality first and works down, so you get the best-looking file that still fits. Only when even low quality is too big does it reduce the dimensions — and it tells you when that happened. Nothing is uploaded; the work happens in your browser.
Good starting dimensions for common limits
If a form also asks for specific dimensions, or you prefer doing it by hand, these are sensible starting points for an ordinary photo saved as JPG at around 75% quality. Busy photos may need a step smaller.
| Limit | Try this width (longest side) | Typical use |
|---|---|---|
| 500 KB | 1,920 px | Web pages, email attachments |
| 200 KB | 1,200–1,600 px | Profile photos, document uploads |
| 100 KB | 1,000–1,200 px | Job and exam application photos |
| 50 KB | 600–800 px | Passport-style photos on forms |
| 20 KB | 300–450 px | Signature uploads, thumbnails |
Signatures are a special case: a dark scribble on a white background compresses extremely well, so a signature can stay quite large and still fit 20 KB. Crop away the empty paper around it first with the image cropper.
Why your photo is still over the limit
- It's a PNG. PNG is lossless and is often five to ten times bigger than a JPG of the same photo. Save photos as JPG.
- It's a screenshot of a photo. Screenshots are saved as PNG at your screen's full resolution. Use the original photo instead, or convert the screenshot with PNG to JPG.
- You only changed the quality. A full 12-megapixel photo rarely gets under 100 KB without losing visible quality. Reduce the dimensions as well.
- The form counts KB differently. Some sites treat 1 KB as 1,000 bytes, others as 1,024. A file of 101,000 bytes is “98.6 KB” to one and “101 KB” to the other. Aim a few kilobytes under the limit, or use the target-size mode, which counts 1 KB as 1,000 bytes so the result passes either way.
- Hidden extra data. Photos carry metadata (camera model, date, GPS location) and sometimes an embedded preview. Re-saving through the compressor drops that, which also keeps your location private.
Watch out for minimum sizes and exact dimensions
Many official forms set a range, like “20–50 KB”, or demand exact dimensions such as 200 × 230 pixels. Squeezing a photo to 8 KB to be safe can get it rejected just as surely as a 2 MB one. Read the requirement carefully, then:
- 1Crop to the required shape first (for example, a portrait photo with your face centered).
- 2Resize to the exact pixel dimensions if the form specifies them.
- 3Compress to the maximum size — the result will sit near the top of the allowed range.
Photos from an iPhone
iPhone photos are often HEIC files, which many upload forms reject outright, whatever the size. Convert them first with the HEIC to JPG converter, then compress the JPG. If HEIC photos won't even open on your computer, see how to open HEIC files on Windows.
Frequently asked questions
How do I reduce a photo to 100 KB without losing quality?
Reduce the dimensions to roughly 1,000–1,200 pixels wide and save as JPG at 70–80% quality. At normal viewing size this looks the same as the original; the detail you lose is only visible when zooming far in.
Can I compress an image to exactly 100 KB?
You can get it just under 100 KB. JPG sizes move in small jumps as quality changes, so landing on exactly 100.0 KB isn't practical — and being slightly under is what upload forms need anyway.
Why does my photo look blurry after compressing?
Usually the quality went too low, or the photo was made very small and then shown larger. Try a slightly lower width with a higher quality instead — for most photos that looks sharper at the same file size.
Should I use JPG or PNG for a 100 KB limit?
JPG for photos — PNG versions are many times larger. PNG only makes sense for simple graphics like logos, and even then check the form accepts it.
Does reducing the file size change the photo's dimensions?
Not if you only lower the quality. In target-size mode, the compressor also reduces the dimensions when quality alone can't reach the limit, and shows the new size.
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