Picture Batch PNG to BMP
PNG to BMP
BMP is what you convert to when something old, embedded or industrial demands it — a machine controller, a scientific instrument, an installer, a piece of software whose file dialog has not changed since Windows 98. It stores every pixel uncompressed, so the files are enormous and there is nothing whatsoever that cannot read one.
Drop PNG images here
PNG files — or any of JPEG, WebP, AVIF, BMP, ICO, TIFF, GIF or camera raw (CR2, CR3, NEF, ARW, DNG, RAF, ORF, RW2). Everything runs on this device.
Your images never leave this device. They are decoded and re-encoded by your own browser, and the security policy on every page blocks this site from sending them anywhere.
Uncompressed Windows bitmap. Huge files, but read by anything, including very old software.
BMP is lossless — it stores every pixel exactly, so there is nothing to trade away.
Images keep their original dimensions.
Kept. BMP stores a full alpha channel, so cut-outs and soft edges come through exactly.
BMP output carries no metadata block, so camera, date and location tags are dropped whichever option you pick.
BMP has nowhere to store Exif metadata, so it is dropped whatever you choose here.
What happens to your image
Expect the file to get much larger. BMP stores every pixel uncompressed, so a 2-megapixel image is about 6 MB whatever it came from.
| Property | Outcome |
|---|---|
| Transparency | Preserved: Kept. BMP stores a full alpha channel, so soft edges and cut-outs survive exactly. |
| Image quality | Preserved: Unchanged. Both formats are lossless, so every pixel comes through exactly. |
| Colour | Partly preserved: Converted to sRGB. Decoding an image colour-manages it into the browser's own space, so the output is sRGB and is left untagged, which every viewer reads as sRGB. A wide-gamut source is reported before conversion. |
| Exif metadata | Not preserved: BMP output from this tool carries no metadata block, so camera and location tags are dropped. |
| Orientation | Preserved: Applied to the pixels, and the tag is reset to upright afterwards so nothing rotates the image a second time. |
Two output shapes, chosen by whether the image needs transparency
An image with no transparent pixels is written as a 24-bit bitmap with a plain BITMAPINFOHEADER. This is the most widely readable BMP there is, and a third smaller than the alternative.
An image with transparency is written as 32-bit with a BITMAPV5HEADER and an explicit alpha mask, tagged sRGB. Declaring the mask is the important part: a 32-bit BMP that does not declare one is genuinely ambiguous — the fourth byte might be transparency or might be padding — and different software guesses differently. Being explicit is what stops the file appearing invisible in one program and correct in another.
Expect the file to get very much larger
There is no compression. A 12-megapixel photograph is a 36 MB BMP whatever it was before, and no setting changes that, because there is no setting. A PNG of the same image might be 8 MB and a JPEG 2 MB.
This is not a defect to work around; it is what the format is. If the size is a problem, the destination probably accepts PNG and you should use that instead.
Rows are written bottom-up
BMP stores its rows from the bottom of the image upwards. A negative height in the header means the opposite, and while both are legal, plenty of readers handle only the conventional one. Output here is bottom-up for that reason.
If something goes wrong
The BMP appears completely transparent or invisible.
A reader that does not understand the alpha mask in a 32-bit bitmap and treats the whole image as transparent.
What to do: Flatten the transparency before converting — set the output to JPEG, or add a background layer in an editor — so the result is 24-bit with no alpha at all.
Software refuses the file as an unsupported bitmap.
Some very old readers understand only the original 40-byte BITMAPINFOHEADER and reject the 124-byte V5 header used for transparency.
What to do: Remove the transparency first, which produces a plain 24-bit BITMAPINFOHEADER bitmap that essentially everything reads.
Questions
Is BMP lossless?
Yes, completely — it stores raw pixels with no compression at all. It is lossless in the same way an uncompressed audio file is: nothing is thrown away, and nothing is saved either.
Does BMP support transparency?
A 32-bit BMP can carry an alpha channel, and one is written here when the image needs it. Support for reading it is patchy in older software, which is why 24-bit is used whenever transparency is not needed.