PNG to BMP converter

PNG → BMP writes an uncompressed 24-bit bitmap, which is why a 20 KB PNG turns into a 2.8 MB BMP and why alpha has to be flattened first.

Converted with Image engine · nothing stored
Free: 5 conversions a day · 5 MB each
Higher limits →

From real runs

What you get — and what changes

Element	Result	What happens
Pixels	Kept	Every opaque pixel of the 1200×800 sample was written unchanged; BMP is lossless.
Transparency	Changed	The PNG's 16,373 transparent pixels were composited onto white (the background option), so the transparent corner became a white corner.
Bit depth	Changed	The BMP is 24-bit RGB with no alpha plane; 32-bit BMP with alpha is not produced.
File size	Changed	20,828 bytes of PNG became 2,880,054 bytes: 1200×800×3 bytes of raw pixels plus a 54-byte header, with no compression.
Metadata	Lost	PNG text chunks, gamma and ICC data have no place in a BMP and are dropped.
Dimensions and orientation	Kept	Width and height are unchanged; the file is written bottom-up as Windows expects and every viewer shows it upright.

Pixels Kept
Every opaque pixel of the 1200×800 sample was written unchanged; BMP is lossless.
Transparency Changed
The PNG's 16,373 transparent pixels were composited onto white (the background option), so the transparent corner became a white corner.
Bit depth Changed
The BMP is 24-bit RGB with no alpha plane; 32-bit BMP with alpha is not produced.
File size Changed
20,828 bytes of PNG became 2,880,054 bytes: 1200×800×3 bytes of raw pixels plus a 54-byte header, with no compression.
Metadata Lost
PNG text chunks, gamma and ICC data have no place in a BMP and are dropped.
Dimensions and orientation Kept
Width and height are unchanged; the file is written bottom-up as Windows expects and every viewer shows it upright.

Sample conversions

Illustration with a transparent corner

Input: sample.png, 1200×800 RGBA, 20,828 bytes, with a transparent triangle in the top-left corner.
Output: 2,880,054-byte 24-bit BMP in 23 ms; the corner is solid white and everything else is pixel-identical.

Same PNG with a black background

Input: The same file with {"background":"#000000"}.
Output: Identical size and pixels except the former transparent area, which is now black.

A real PNG → BMP run

We converted our PNG sample (20 KB) with Image engine on 2026-10-20. It took 54 ms and produced a 2.7 MB BMP file, 138× larger than the input. The engine raised 1 warning, listed below.

Input · sample.png · 20 KB

1200 × 800 px, 8-bit, colour type 6

Width: 1,200
Height: 800
Encoding: 8-bit, colour type 6

Output · sample.bmp · 2.7 MB

1200 × 800 px, 24-bit

Width: 1,200
Height: 800
Encoding: 24-bit

Image metadata stripped from output.

Options and when to change them

background: Pick the colour that transparent areas should become; white is the default and black suits dark UIs.
width: Reduce the size before converting; BMP bytes grow with pixel count and nothing else.
fit: Use cover when a fixed-size bitmap is required by an installer or a boot screen.

Do it yourself

Pillow

bash

from PIL import Image

img = Image.open("in.png").convert("RGBA")
bg = Image.new("RGBA", img.size, "#ffffff")
bg.alpha_composite(img)
bg.convert("RGB").save("out.bmp")

Saving RGBA directly writes a 32-bit BMP that many Windows tools misread; flatten first.

ImageMagick

bash

magick in.png -background white -flatten -type TrueColor BMP3:out.bmp

BMP3 avoids the newer header variants some old software rejects.

PNG to BMP by API or MCP

The HTTP API and the MCP server run the exact engine this page uses (Image engine); the response carries the same warnings the web converter shows. Check support first with GET /api/v1/pairs?from=png&to=bmp.

curl

curl -X POST https://filetypeconverters.com/api/v1/convert \
  -H "Authorization: Bearer $FTC_API_KEY" \
  -F "file=@input.png" -F "from=png" -F "to=bmp" \
  -F 'options={"dpi":96}' \
  --output output.bmp

Options this engine accepts for PNG → BMP

Key	Applies to	Type	Default
dpi	Reading PNG	number	96
width	Writing BMP	number	0
height	Writing BMP	number	0
fit	Writing BMP	contain · cover · fill	contain
quality	Writing BMP	number	90
background	Writing BMP	string	#ffffff
stripMetadata	Writing BMP	boolean	true

API reference

When this is the wrong conversion

If a program only needs a lossless image, keep the PNG; it is the same pixels at a fraction of the bytes.
If transparency matters, BMP is the wrong container; PNG, WebP and TIFF keep alpha.
If the target is an icon, PNG → ICO produces the proper resource instead of a bitmap you would still have to wrap.

PNG to BMP questions

Why is the BMP 138 times bigger than the PNG?

BMP stores three uncompressed bytes per pixel. 1200×800 pixels is 2,880,000 bytes before the 54-byte header, however simple the picture; PNG compressed the same flat colours to 20,828 bytes.

What happens to transparent areas?

They are filled with the background colour, white unless you set another. BMP as written here has no alpha channel to keep them transparent.

Is the output an 8-bit or a 24-bit bitmap?

24-bit true colour. Palette-based 8-bit BMPs are not produced; convert with a tool that supports -colors if a legacy program insists on one.