Calculate image file size online
Find out how much an image's format and compression are actually doing for it — its real file size, next to what those same pixels would cost stored raw, with no compression at all. Add your images and download a small report for each.
The uncompressed figure is what a browser would need to hold every pixel with no encoding at all: width × height × 3 bytes for an opaque image, ×4 if it carries transparency. Comparing that to the real file size is what shows you the compression already happening — often 90%+ for an ordinary JPG photo.
Your images never leave your device. The calculation runs entirely in your browser, so nothing is uploaded, stored, or scanned, and a batch costs no more than a single file.
or drop them here — nothing is uploaded
How to image file size calculator
Add your images
Drop JPG, PNG, or WebP files into the box, or click to browse.
Calculate and download
Press Image File Size Calculator. A small text report downloads for each image, and the result also shows on screen.
Frequently asked questions
Are my images uploaded anywhere?
No. The calculation runs in your browser using JavaScript, so your files stay on your device. You can confirm this by opening your browser devtools Network tab while working — there are no upload requests.
What is the 'uncompressed' size actually measuring?
The storage every pixel would need with absolutely no encoding — 3 bytes per pixel for red, green, and blue, or 4 if the image has transparency. No real file is ever stored this way; it exists purely as a baseline, to show what JPG, PNG, or WebP's compression is actually saving you.
Why is a PNG closer to the uncompressed figure than a JPG?
Because PNG compresses losslessly — it can shrink flat colour and repetition, but it cannot approximate detail away the way JPG does. A photo saved as PNG will sit much closer to the raw figure than the same photo saved as JPG, which is exactly why JPG exists for photographs.
Can this predict the size after I compress or resize an image?
No — it reports the file as it is now. Compress Image will show you the real result of an actual compression pass, which is more accurate than any estimate.
Is there a limit on how many files?
Thirty at a time, which is a limit of your device rather than our policy — everything is held in memory while it works.