JPG to BMP converter

Content last reviewed:2026-09-07

You add your JPG photos and download uncompressed bitmaps written at 24 bits per pixel. You know the weight of the result in advance: a 3000 by 2000 pixel photo gives a 17.2 MB file whatever it happens to show. All the work happens inside your browser.

Files in queue

Add JPG files on the left to start converting to BMP.

What is BMP and what is JPG?

BMP writes an image point by point, exactly as it is meant to appear on screen. The format was built for OS/2 and later moved into the Windows interface, and since no patents weigh on it, every platform reads it today.[1] Microsoft describes the shape of such a file plainly: first comes a header with the file size and the offset where the image begins, then a second header with the dimensions and the number of bits per pixel, then an optional colour table, and at the end the raw array of points.[2]

This tool writes one variant of that format: 24 bits per pixel, without compression, with a 40-byte BITMAPINFOHEADER.[3] It is the most widely read variant of BMP, so any program that knows the format at all will open it.

JPG stands on the other side. The name is the abbreviation of the Joint Photographic Experts Group, and the way of writing is set out in Recommendation ITU-T T.81, approved in September 1992.[4] The encoder splits the image into blocks of 8 by 8 pixels and drops the detail inside them that the eye will not catch at normal viewing. That is what keeps the file small and lets a camera photo fit on a memory card.

Writing to BMP turns that order around. Every pixel gets its own three bytes in the file, so the weight of the result follows from the dimensions of the image alone.[5]

How do you convert JPG to BMP?

Drag your JPG files onto the Add files area, or click it and pick the images from your drive. Then press the Convert button. The quality here is fixed and as high as it gets, because the writing runs without compression.

You can download the finished images one at a time with the Download button on a queue row, or all together with Download all. The Clear all button empties the queue, and the Remove label on a row takes a single file out of it.

In the queue on the right, every file shows its weight before and after the conversion along with the difference in per cent. Since BMP is heavier than JPG, the line under the buttons reads Increased, carrying the number of megabytes and the percentage the file has gained.

The writing itself is done by our own encoder, running on your computer. The browser cannot write BMP from the canvas: the MDN documentation describes this behaviour plainly — with a format the browser does not know, you get a PNG file and no warning.[6] So we put the header and the pixel data together ourselves, and the image stays on your device from the first click to the end of the work.

Under the converter sits a format switch reading JPG to BMP. Clicking either of the two formats opens a list, and picking from it takes you to the converter page for that pair. Every pair in this group is also gathered on the Format conversion page.

How much does a BMP file weigh and how do you know in advance?

The weight of a BMP file follows from the dimensions of the image alone. Every pixel takes three bytes, and every row is padded with zeros up to a full four bytes; the Microsoft documentation gives a ready formula for it.[3] On top of that come 54 bytes of header. This arithmetic looks the same for every image, whatever the photo happens to show.

Let us follow it on a photo measuring 3000 by 2000 pixels. One row holds 3000 pixels at three bytes each, which makes 9000 bytes. At that width nothing needs padding. There are 2000 rows, so the pixels alone take 18,000,000 bytes. Together with the header the file weighs 18,000,054 bytes, which is 17.2 MB in the notation the summary inside the tool uses.

The row padding only shows up at widths that do not divide by four. An image 1001 pixels wide holds 3003 bytes of data in a row, and the file sets aside 3004 bytes for it. That one byte comes back in every row of the image.

So the gain over the source file depends only on how hard that file was compressed before. A photo that weighed 1.52 MB as a JPG weighs 17.2 MB as a BMP, which is 11.3 times more.

How much does the same image weigh in JPG and in BMP?

We passed the JPG files through this converter and set the weight of the input next to the weight of the result. The weights are given exactly as the tool counts them: in kilobytes and megabytes of 1024, with the same rounding.

Image	Size in pixels	JPG	BMP	Times larger
Camera photograph	3000 × 2000	1.52 MB	17.2 MB	11.3
Photo for a web page	1280 × 850	260.9 KB	3.11 MB	12.2
Scanned document	1200 × 1600	309.9 KB	5.49 MB	18.2
Interface screenshot	1200 × 630	55.8 KB	2.16 MB	39.7
Graphic of flat colour areas	800 × 600	14.1 KB	1.37 MB	99.4

Our own measurement from 5 September 2026, taken in a browser built on the Chromium engine. The BMP column matches the formula from the Microsoft documentation to the byte, so you can work out the weight of the result yourself before you drop a file into the queue.

How much room does a bitmap take at common sizes?

Weights worked out from the formula for a 24-bit file: 54 bytes of header plus the width rounded up to a multiple of four bytes, times the number of rows.

Image size	Size in pixels	BMP file weight
Interface icon	256 × 256	192.1 KB
Photo for a web page	1280 × 850	3.11 MB
A Full HD screen	1920 × 1080	5.93 MB
An A4 page scanned at 300 points per inch	2480 × 3508	24.9 MB
A photo from a 12 megapixel sensor	4000 × 3000	34.3 MB
A 4K screen	3840 × 2160	23.7 MB
The largest file the converter takes	5900 × 5900	99.6 MB

The last row shows the limit of the tool from the other side: at around 5900 pixels per side the result reaches the 100 MB cap the converter puts on a single file.

How does JPG differ from BMP?

Format property	JPG	BMP
How the image is written	Lossy compression on blocks of 8 × 8 pixels	Pixel values in full, point by point
The weight of the result depends on the image content	Yes	No, on the dimensions alone
Colour depth	8 bits per colour component	1 to 32 bits per pixel, 24 here
Alpha channel, meaning transparency	No	Yes, in the 32-bit variant; this converter writes the 24-bit one
Lossless compression	Yes, in a separate mode set out in the standard	Yes, by RLE on palette images
Camera data (EXIF)	Yes, in a separate file segment	No
From which browser version they are read	from the first versions of Chrome, Firefox, Safari and Edge	from the first versions of Chrome, Firefox, Safari and Edge
Weight of a 3000 × 2000 pixel image	1.52 MB at 85% quality	17.2 MB always

The BMP properties come from the Microsoft documentation[2] and the encyclopaedia entry on that format[1], the JPG properties from Recommendation ITU-T T.81[4] and the MDN guide, which describes both formats as read by every browser.[5] The weights in the last row come from our own measurement.

What does the converter do with a JPG file?

Seven things worth knowing before you drop a larger batch of images into the queue.

It writes 24 bits per pixel, without compression
The result carries a 40-byte BITMAPINFOHEADER, rows running from the bottom up and padding to four bytes. This is the same shape Firefox writes in its own canvas encoder, and the most widely read variant of the format.
The pixel count stays the same
A 3000 by 2000 pixel image comes out as a BMP measuring 3000 by 2000 pixels. Only the way of writing changes, while the frame and the resolution are left untouched.
The image looks exactly as it did
The converter copies out the pixels read from the JPG file, so the screen shows you the very same thing. The compression blocks that appeared when the file was written as a JPG stay in the image for good: BMP will keep them as faithfully as it keeps the rest.
Colour is written at eight bits per channel
The browser canvas works with eight bits for red, green and blue, and a 24-bit BMP carries exactly as many. A typical monitor shows that same range.
The writing takes a fraction of a second
The encoder runs on your own computer, so the time depends on its power. Files from the queue go one after another, and the bar above the buttons shows how many of them are already finished.
Single files up to 100 MB
That is what the converter takes from one file. Above that size, the message reads File is too large (max 100 MB). The limit applies to the input file, while the result can be eleven to a hundred times heavier, so with large photos it pays to work the weight out from the formula first.
Very large images are fitted to the canvas
The browser canvas holds 16,384 pixels per side and around 268 million pixels in total. An image beyond that limit is scaled down proportionally by the tool, so that all of it fits into the result.

When should you pick BMP and when another format?

An older program or device opens the file
When a program or a device reads BMP and nothing else, 24-bit without compression is the safest of the format’s variants: the reader gets a ready array of pixels and handles it without palette support and without RLE unpacking.
The image goes into your own program
A raw array of pixels reads in a few lines of code, with no decoding library. That is why BMP turns up as a working format in image processing and in tests.
The way back
You can turn a finished bitmap back into a light photo with the BMP to JPG converter. It is the same pair of formats, only reversed.
The file has to keep its transparency
Writing at 24 bits describes every pixel as fully opaque. When a cut-out background is meant to stay cut out, reach for the JPG to PNG converter, which writes losslessly and does carry an alpha channel.
The image goes onto a web page
Here the weight of the file counts, and the MDN guide advises plainly against using BMP for website content. A lighter file comes from the JPG to WebP converter or the JPG to AVIF converter.
The scan goes to an office or an archive
A scanned page is easier to send as a PDF than as an image. The JPG to PDF converter will make one: it lays every image on a separate A4 page, matching the orientation to the proportions of the file.

Convert other files to BMP

AVIF to BMP PNG to BMP WebP to BMP TIFF to BMP

Convert JPG to other formats

JPG to PNG JPG to WebP JPG to AVIF JPG to GIF JPG to TIFF JPG to PDF JPG to Base64

Sources

BMP file format — Wikipedia
Bitmap Storage — Microsoft Learn
BITMAPINFOHEADER — Microsoft Learn
Recommendation ITU-T T.81, September 1992 — International Telecommunication Union
Image file type and format guide — MDN Web Docs
HTMLCanvasElement: toBlob() method — MDN Web Docs

The file sizes in the tables come from the formula the encoder in this tool writes by, and we checked them on finished files. What the page says about either format rests on the sources listed above.

Content last reviewed: September 7, 2026 · written and checked by the Arteon team

Common questions about converting JPG to BMP

Why is a BMP file so many times larger than a JPG?

Because BMP keeps the value of every pixel in full, while JPG simplifies it. In our measurement the camera photograph went in as 1.52 MB and came out as 17.2 MB, which is 11.3 times more. The graphic made of flat colour areas grew from 14.1 KB to 1.37 MB, because in JPG such areas can be described very briefly, while in BMP every point takes its own three bytes. When you care about a light file, the same pair the other way round runs through the BMP to JPG converter.

Will converting JPG to BMP improve the quality of the photo?

The image looks the same. The converter copies out the pixels that are in the JPG file, and those came into being after compression. Blocks and softening from the earlier writing stay in the image, and BMP will keep them as faithfully as it keeps the rest. What you gain is a format that simplifies nothing further on the next save.

How much will my file weigh after the conversion?

You can work it out in advance, because the weight depends on the dimensions alone. Multiply the width by three bytes, round up to a multiple of four, multiply by the number of rows and add 54 bytes of header. A Full HD screen, meaning 1920 by 1080 pixels, gives 5.93 MB. An A4 page scanned at 300 points per inch gives 24.9 MB.

Do my files go to a server?

No. The page code in your browser loads the image, draws it on the canvas (the Canvas API) and hands it from there to our encoder, which also runs locally. The file stays on your device for the whole time you work, and once you close the tab it leaves the browser memory.

Why does writing BMP need an encoder of its own?

Because the browser does not write this format. The canvas accepts a request to write BMP only in Firefox, while Chrome, Edge and Safari quietly hand back a PNG file with a .bmp extension. The MDN documentation describes this behaviour plainly. Our encoder puts the header and the pixel data together on its own, so the result is a real BMP file in every browser.

What happens to the camera data, meaning EXIF?

It stays in the source file. The BMP format has no room for it in its structure, and the image passes through the browser canvas, so what reaches the result is the image itself. When you want the date, the camera model and the coordinates gone from a photo, this conversion does it along the way.

How many files can I convert at once?

You can add as many files to the queue as you like, and the tool works through them one by one while showing the progress above the buttons. A single input file can weigh up to 100 MB, and the total number of files depends on the memory of your device.

Will a BMP file open on a phone?

Yes. The MDN guide lists BMP as a format read by every version of Chrome, Edge, Firefox, Opera and Safari, so you will open it in a browser on a phone as well. The system gallery tends to be fussier about it than the browser, and at a weight of a dozen or so megabytes such a file is awkward to send through a messenger. The remaining ways of writing an image, and the moves between them, are gathered on the Format conversion page.