Drop images to fit a KB rangeAdd images to fit a KB range
Set a minimum and a maximum, and see which files land inside.
or paste with CtrlCommandV JPG, PNG, WebP, AVIF, GIF or BMP
Your files never leave your deviceAbout this tool
Reduce image size in KB, between any two sizes
Type the smallest and largest size you’re allowed, add your images and press Compress. ToolHero aims each file just under the maximum at the best quality it can, resizing only if needed. A file that comes out below the minimum is marked on its card, because padding it with empty bytes wouldn’t add any detail.
Three ranges on our test files
Each file compressed once, aiming at the top of its range.
- 12 MP phone photo, 10 to 30 KB 3024×4032, 5.17 MB → 462×616 at quality 42 29,826 bytes
- A4 scan at 300 dpi, 100 to 150 KB 2480×3508, 3.22 MB → 1622×2294 at quality 54 148,193 bytes
- Signature, 50 to 100 KB Fits at full size and quality 75, so it’s flagged as under 50 KB 38,702 bytes
A range, not just a limit
Many sites state both ends: “between 20 KB and 50 KB”. The maximum is the hard part, and it’s what ToolHero works towards. It keeps the highest quality it can, never drops below quality 40, and scales an image down only when that still doesn’t fit, so each file lands close under the top of your range.
The minimum is a check. After compressing, every file below it says so on its card, so you know before you send it.
When a file comes out under the minimum
It happens with simple pictures, such as a signature on white paper, and with images that were small to begin with. Our signature fitted a 100 KB maximum at full size and quality 75, yet only reached 38.7 KB.
- Start from a bigger original. A larger scan or the camera’s full photo has more real detail to keep.
- Pick a higher quality. On the Compress page, Quality mode lets you go above 75, which makes files larger.
How many pixels a size buys
For a 12 MP phone photo, keeping 600 pixels on the long edge takes about 30 KB: in our test it came out at 462×616. Below that, photos turn into thumbnails. Documents go further, because white paper costs almost nothing: an A4 scan kept 1622×2294 pixels in 150 KB, around 196 pixels per inch.
How it works
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Step 1:Set the range
Enter the maximum size and, if the site has one, the minimum. JPG and Allow smaller dimensions are already on.
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Step 2:Add images and compress
Drop in one file or a whole batch, then press Compress. Each file is fitted on its own.
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Step 3:Check every card
Files under your minimum are flagged; the rest are ready. Download them one at a time or as a .zip.
Kilobytes, kibibytes and which one a site means
There are two kilobytes in use. The decimal one is 1,000 bytes, used by most operating systems, phones and websites. The binary one, properly called a kibibyte (KiB), is 1,024 bytes and still turns up in older software.
ToolHero shows and aims at decimal sizes. A maximum met in decimal bytes is always met in binary ones too, because a kibibyte is bigger. A minimum works the other way, so if a site’s minimum is strict, set yours a few KB higher.
Questions, answered
What does the minimum size actually do?
It checks the results. Compressing always aims at the maximum, and any file that ends up smaller than your minimum is marked on its card. Leave the minimum empty if the site only has a maximum.
Why won’t ToolHero make an image larger in KB?
Because extra bytes on their own add no detail; they only make the file heavier. A larger, sharper file has to come from a bigger original or a higher quality setting.
Which page should I use for a single size limit?
Use the page for that size: 20, 50, 100 or 200 KB. Each opens with its size set and shows what it did to our test files. This page is for limits with a minimum and a maximum.
Does ToolHero count 1 KB as 1,000 or 1,024 bytes?
1,000 bytes, as most websites and operating systems do. That keeps every maximum safe under either definition.
Can I fit images to a range in MB instead of KB?
Yes. Switch the unit next to the maximum to MB and both sizes follow, for example 0.5 to 1 MB.
Pages for one size
Format
Opens everywhere. No transparency.
Compression
We find the highest quality that fits, and shrink the image only if it still doesn’t.
When even the lowest quality is too big, the image is scaled down until it fits.
We never add bytes: a file that comes out smaller says so.