KB Resize: Resize an Image to Any Size in KB
Set a limit in KB, add your photos, and download files that are guaranteed to be under it. Everything happens in your browser.
More options: pixel size, DPI, how KB is counted
Leave width and height empty to let the tool choose. Fill in one of them to keep the proportions; fill in both for an exact size.
How the KB resizer works
A photo’s file size depends on two things: how many pixels it has and how strongly those pixels are compressed. The resizer adjusts both, in the order that keeps your picture looking best:
- Quality first. It saves the image as JPG and searches for the highest quality setting that still fits under your limit. A search takes a handful of tries instead of dozens, because each try halves the range of possible settings.
- Pixels only if needed. If even a fairly low quality is too big, it reduces the width and height in proportion, then goes back to finding the best quality at that size.
- Measured, not estimated. The size you see is the size of the exact file you download. It lands just under the maximum, usually within about 3%, so you keep as much quality as the limit allows.
Options, explained
| Option | What it does |
|---|---|
| Target size (maximum) | The file will never be larger than this. Switch the unit to MB for larger targets. |
| Minimum size | For forms that say “between 20 KB and 50 KB”. The tool raises quality, and can enlarge the picture if you allow it, to get above the minimum. It never pads the file with empty data. |
| Save as | JPG is the right choice for photos and the most widely accepted. PNG is lossless, so it can only shrink by using fewer pixels. WebP files are often smaller than JPG at similar quality, but many forms don’t accept WebP. |
| Width and height | Give both for an exact size in pixels (the photo is cropped or padded to that shape), or one to keep the proportions. |
| DPI | Writes a dots-per-inch value into the JPG header. It doesn’t change the pixels or the file size. See resizing in cm for when it matters. |
| How to count a KB | Safe mode (default) satisfies forms that count 1 KB as either 1,000 or 1,024 bytes. Pick one convention if you know which your form uses. |
KB, kB and KiB: why the numbers can disagree
In the metric system a kilobyte (kB) is 1,000 bytes. Computer memory grew up in powers of two, so 1,024 bytes also came to be called a kilobyte; the international standard name for that unit is the kibibyte (KiB). A 50,500-byte file is therefore 50.5 kB but only 49.3 KiB, and it would pass one form’s “50 KB” limit and fail another’s. Each result here lists the exact bytes plus both readings, so you can compare them with whatever your form reports.
Pick a ready-made target
Each of these pages presets the tool and explains what that particular size can realistically hold: 20 KB for very small uploads, 50 KB, 100 KB for documents and scans, 200 KB and 1 MB. If a form asks for a bigger file, use increase image size in KB; for signatures there’s a signature resizer that also cleans up the background.
Limitations
- HEIC photos open only in browsers that support the format; most don’t. Convert to JPG first.
- Very large files: up to 50 MB and 120 megapixels per image. Pictures above 16 megapixels are scaled down to 16 megapixels before the search starts, so they fit in a browser’s memory on phones as well as computers.
- Animated GIFs become a single still image.
- Tiny limits need tiny pictures. At 10 KB or less, expect the tool to reduce the pixel dimensions substantially.
- Metadata is removed. The saved file doesn’t carry the original’s EXIF data (camera details, GPS location). That saves bytes and protects your privacy, but if you need the metadata, keep the original.
Frequently asked questions
How do I resize an image to a specific size in KB?
Type the maximum size (for example 50 KB), optionally a minimum, then choose your images. The tool tries different JPG quality levels and, only if needed, smaller pixel dimensions until the file is just under your limit, then shows the exact size before you download it.
Will the file really be under the limit I type?
Yes. Every result is measured on the actual file that you download, byte for byte, and the tool will not offer a file that is over the maximum. By default it also counts a KB the strict way (1,000 bytes for the maximum) so the file passes forms that use either convention.
Is 1 KB 1000 or 1024 bytes?
Both are in use. The decimal kilobyte (kB) is 1,000 bytes; the binary unit, officially called a kibibyte (KiB), is 1,024 bytes, and many programs label it KB. Because upload forms don't always say which they mean, the default setting here keeps the file under the smaller reading of the maximum and above the larger reading of the minimum.
Are my photos uploaded to a server?
No. The images are opened, resized and saved by your own browser. They never leave your device.
Can I resize several images at once?
Yes. Choose or drop up to 30 images; each one is resized to the same target in turn, and you can download them one by one or all together as a ZIP file.
Why is my file smaller than the target?
If your image already fits at high quality, the tool stops there rather than inflating the file. Being under a maximum is what forms check. If your form also has a minimum, type it in the minimum box and the tool will aim between the two.
Why can't it open my iPhone photo?
iPhones often save photos as HEIC, which most browsers can't open. Convert the photo to JPG on the phone first (or switch the camera to 'Most Compatible' in Settings → Camera → Formats) and then choose the JPG here.