What quality should I use when converting PNG to JPEG: keep 90 or go lower?

What the quality number really means

The slider runs from 1 to 100 and starts at 90. The number is not a percentage of the original. It becomes a value between 0.01 and 1 that the browser passes to its JPEG encoder: 90 becomes 0.9, 75 becomes 0.75, and the top of the scale, 100, becomes 1. The higher the value, the more detail the encoder keeps and the bigger the file. No setting makes JPEG lossless; even 100 gives up a little.

Note that the slider only appears for JPEG and WebP. Pick PNG and it disappears, because PNG loses nothing and has no quality setting.

A quick guide by use

• An image going to a client, to print, or to be edited later: 90 or above.
• Product photos for a store page: try 80 to 85; the difference from 90 is rarely visible on screen.
• Thumbnails and large banner backgrounds: 75 is often fine.
• Images with small text or figures, such as a table screenshot: stay at 90 or more, since lettering suffers first.

How to compare quickly

1. Add one PNG that is typical of your images to the Image format converter and choose JPEG.
2. At 90, read the size in the file's row, then zoom into the preview and check edges and smooth areas.
3. Move the slider to 80. The tool reconverts automatically a moment later and shows the new size.
4. If you see no difference in the preview and the saving matters to you, use the lower value for the whole batch.

Why 90 is the safe choice for conversion in particular

Converting from PNG starts from a full-detail image, so whatever JPEG throws away is thrown away once, here. Choose 70 today and need a better image tomorrow, and you cannot get it out of that JPEG; you would have to go back to the PNG. So make the first converted copy generous, and make smaller copies from it or from the original as needed.

If the PNG is transparent, remember the background color field next to the slider. Quality has nothing to do with it: transparent areas get filled with the chosen color whatever the quality.

When to use the compressor instead

The converter is built to change formats. If your images are already JPEG and you want them smaller, the converter will leave them alone because they are already in the target format. That is a job for the Image compressor, which re-encodes JPEGs at the quality you choose and shows the saving.