Compress an image to an exact file size
Type the limit your form or website asks for, like 50 KB or 2 MB. Graviton finds the highest quality that fits under it, on your device, so you never have to guess at a quality setting.
How it works
A search, not a guess
A quality slider can’t tell you how big the file will be. Exact file size works the other way round: you set the size, and Graviton finds the quality.
- 1
Set a maximum size
Exact file size is the first goal and the homepage default. Type a limit in KB or MB, or pick a preset: 20 KB, 50 KB, 100 KB, 200 KB, 500 KB, 1 MB or 2 MB.
- 2
Graviton searches for the best quality
It encodes your image several times, each time closer to the target, and keeps the highest quality that stays under it.
- 3
Dimensions stay unless you allow shrinking
Graviton keeps the original width and height. If fitting needs very heavy compression, it offers to shrink the dimensions a little at a time instead, which looks better than heavy artifacts.
Sizes are counted in kilobytes of 1,000 bytes, the stricter way to count, so a file that passes here also passes forms that count 1,024 bytes per kilobyte. For large photos, Graviton first tests a small copy to predict the right quality, so most images settle after a few encodes. If you want to understand the trade-off it is making, read image quality vs file size.
Common limits
Size limits you will run into
Forms, portals and email services all set different maximums. These are typical ones; always check the exact number on yours.
| Where | Typical limit | Tool |
|---|---|---|
| Signatures on exam and job applications | 10–20 KB | Compress a signature to 20 KB |
| Exam, ID and job portal photos | 20–50 KB | Compress a photo for exam and job forms |
| Visa, ID and job application photos | 100 KB | Compress an image to 100 KB |
| Scanned documents for applications | 200 KB | Compress an image to 200 KB |
| Website uploads, marketplaces and avatars | 500 KB | Compress an image to 500 KB |
| Email attachments and chat uploads | 1 MB | Compress an image to 1 MB |
| Upload forms, job sites and online stores | 2 MB | Compress an image to 2 MB |
Need a different number? Compress an image to any size in KB and type it in.
Details
What happens at the edges
Most images fit on the first search. These are the cases where Graviton has to make a choice, and how you control it.
Shrink dimensions if needed
Off by default, so your width and height stay the same and Graviton only lowers quality. If that needs quality below about 40, a note offers a one-click “Shrink dimensions to fit”. Turn the setting on to let Graviton reduce the dimensions whenever even low quality is too big.
When an image can’t fit
If no setting gets under the target, you get the smallest version Graviton could make, clearly marked, with a one-click “Shrink dimensions to fit”. You can also try another format.
When it already fits
If your image is already under the target and you kept its format, Graviton returns the original file unchanged instead of compressing it again.
Any output format
Size tools save JPG by default, because almost every form accepts it. WebP, AVIF and PNG work too; PNG reaches a size by using fewer colors. GIFs keep every frame.
Exact file size works with batches too, which helps when a store or portal wants every image under the same limit. See bulk compression for how batches and ZIP downloads work, and every setting, explained for how size targets combine with format and resize.
FAQ
Exact file size questions
Will the file be exactly the size I type?
It will be that size or slightly under. Graviton keeps the highest quality that fits, so most files land just below the target.
Is 1 KB 1,000 or 1,024 bytes?
Graviton counts 1 KB as 1,000 bytes and 1 MB as 1,000,000 bytes, the stricter of the two. A file under 50 KB here is also under 50 KB on a form that counts 1,024 bytes per kilobyte.
Why did the width and height of my image change?
Because “Shrink dimensions if needed” was on, either because you turned it on or clicked “Shrink dimensions to fit”, and even low quality was too big at full size. Turn it off to keep the original dimensions; the file may then need heavy compression or stay above the target.
Can I compress a whole batch to the same size?
Yes. Drop up to 250 images and each one is brought under the target on its own. Download them one by one or together as a ZIP.
Does trying a different target use up my daily limit?
No. Compressing is unlimited and never counts; only downloads do. Downloading the same image again on the same day, on the same device, counts once, whatever target or settings you use. Free accounts include 3 downloads a day, and Pro has no daily limit.
Tools for this
Each one opens the compressor with a size target already set. You can change it any time.
Hit your size limit on the first try
Type the size, drop your image and download a file that fits. A free account includes 3 downloads a day.