Does converting a JPG to PNG improve its quality, and why is the PNG so much bigger?
No, converting to PNG does not improve quality. PNG stores the pixels exactly as they are, including any blur and small blocks that JPEG compression already created. The size jump is normal too, because PNG was not designed to compress photographs, and the tool shows you the real increase and notes that it is expected.
Where the 'PNG is better' idea comes from
People hear that PNG is lossless and assume that converting a picture to it restores something. Lossless means PNG will not add new loss; it does not mean it gives back what was lost before. Your JPG lost some detail the moment it was first saved, and that detail no longer exists anywhere in the file, so no format can recover it.
Open both versions side by side and zoom in: you will find the same smudges around lettering and the same banding in a sky or a plain backdrop. The only difference is that the PNG preserves those flaws with perfect accuracy.
Why the file balloons
JPEG was built for photographs. It throws away fine detail your eye barely notices, which makes files small. PNG tries to compress without throwing anything away, which works well on graphics with flat colors and badly on pictures full of gradients and sensor noise, such as product shots and portraits.
A 673.8 KB JPG product photo converted to PNG came out at 2.96 MB.
The tool's row reads: 349.3% larger than the original, with a note that this is expected when a photograph is converted to PNG.
On screen: identical to the original, neither better nor worse.
In other words, you paid more than four times the size for nothing visible. On a store page with dozens of images, that means slower loading for your visitors with no benefit.
When converting JPG to PNG does make sense
- When a program or an organisation specifically requires PNG. You convert to meet the requirement, not to improve the picture.
- When you want a working copy you will edit and save many times. Every JPG save loses a little more, while PNG saves lose nothing.
- When the image is a screenshot or a simple graphic that was saved as JPG by mistake. Its PNG size will not explode the same way.
If what you really want is a sharper picture
Go back to the source: the original photo from the camera or phone, or the design file before it was exported. That is the copy that holds the detail. And if your real goal is a lighter file rather than a sharper one, keep the JPG and compress it with the Image compressor, or try WebP in the Image format converter at quality 80 or 90 and compare the sizes.
Common questions
Does converting to PNG harm the image?
It adds no loss, but it gives you a much heavier file with no improvement. Always keep the original.
Why is there no quality slider when I pick PNG?
PNG is lossless, so there is nothing to set. The slider appears for JPEG and WebP only.