Rotate BMP Bitmap Free Online Secure
The picture is turned and saved again. Nothing is scaled, nothing is cropped, and the file never leaves your device.
Work on your PDF
Drop a BMP here, or choose one.
Your file never leaves this device. Everything runs in your browser.
Nothing uploaded
Why a photo can be sideways in the first place
A camera sensor is rectangular and does not turn when you turn the camera. When you hold a phone upright, the picture is still recorded in the sensor's own orientation, and a small tag is written into the file saying which way up it should be shown. That tag is part of EXIF, the block of camera data that has travelled inside photographs since 1995. Software that reads the tag shows the photograph upright; software that ignores it shows the sensor's version, lying on its side. This is why the same file looks right on your phone and wrong when uploaded somewhere, and it is the reason most rotation is needed at all.
Where you need it
Scans that came out of the feeder the wrong way up; photographs taken in portrait that every program insists on showing in landscape; a PDF whose pages were scanned sideways and are painful to read; a document whose first page is upright and whose appendix, scanned separately, is not. Rotation is also the quickest cure when a file has to be sent somewhere that will not read the orientation tag.
Questions people ask
Why does my photo look right on my phone but sideways on the computer?
Because the two are reading the same file differently. The photograph is stored in the sensor's orientation with a tag saying how to turn it; the phone obeys the tag, and the other program does not. Rotating the image here resolves the disagreement permanently: the pixels themselves are turned and the tag is set to upright, so every program agrees from then on, whether it reads the tag or not.
Does rotating lose quality?
Not in a quarter turn. A rotation by 90, 180 or 270 degrees moves whole pixels into new places without having to invent any, so the image that comes out is exactly the image that went in. Rotation by some other angle is a different matter: the new grid does not line up with the old one, every pixel has to be estimated from its neighbours, and the picture softens slightly. The pages here turn in quarter turns, so nothing is lost.
Does the file lose quality?
It depends on what the two formats can hold. Converting between formats that store the same thing — a PNG to a BMP, a WAV to a FLAC — loses nothing. Converting into a format that throws information away to save space, such as JPEG or MP3, loses a little every time, and converting back does not bring it back. Where a choice exists, this page errs towards keeping the original quality rather than making the smallest file.
Is my file uploaded anywhere?
No. The conversion happens inside your browser, on your own machine; the file never leaves it and there is no server here that could receive it. That is why a large file is limited by your own memory rather than by an upload, and why nothing you convert can appear in anybody's logs — including ours. The audio and video tools do fetch their conversion engine from this site the first time you use them, some thirty megabytes once; after that the work still happens entirely on your machine.
Why people rotate BMP files
BMP files come from older scanners, legacy software, instruments and archives, and they have a habit of arriving the wrong way round. A scanned page stored on its side. A picture from a piece of equipment that always writes its images in one orientation. A screenshot from an old program. When the picture is not upright, you need to rotate the BMP so that it reads correctly, and ideally you want to do it without installing anything or learning a new program. That is what this page is for: you drop the file in, choose a turn and download the corrected picture.
People rotate BMP files for very practical reasons. A scan has to go into a document and must be upright. A picture is to be published and should not make readers tilt their heads. A batch of images from a measuring device needs to match the orientation of the reports they illustrate. Because BMP is an old and unfashionable format, many modern tools do not even offer to turn it, which is why a simple browser-based way to rotate a BMP is so welcome.
This page lets you rotate BMP files entirely in your browser. The picture never leaves your device, which matters for scans of documents and instrument images. Below you will find how the rotation works, why the result is a PNG rather than a BMP, what is kept and how to avoid the usual mistakes.
How the rotation works
The picture is turned and saved again
To rotate a BMP here, you choose a turn, and the picture is turned and written out again as a new file. Nothing is scaled and nothing is cropped. A picture of 2000 by 1500 pixels, turned a quarter, becomes 1500 by 2000 pixels, with every pixel simply in a new place.
Whole quarter turns only
You can turn a picture a quarter to the right, a quarter to the left or half a turn. These cover the sideways and upside-down cases that make up nearly all real needs. A picture that is only slightly crooked needs a different kind of tool, one that straightens by a few degrees.
How to tell which way to turn
Look at the picture: if the top of the scene points to the right, it needs a quarter turn to the left to be upright; if the top points to the left, a quarter turn to the right; if it is upside down, a half turn. When in doubt, try one and look at the preview.
Why the result is a PNG
A browser cannot write BMP
Here is the one thing to know about this page. A browser can read a BMP but cannot write one. So when you rotate a BMP here, the corrected picture is saved as a PNG. The picture is identical, with every pixel the same, but the wrapper is not: you receive a .png file, not a .bmp. For nearly every modern purpose that is better, since PNG is accepted everywhere and is far smaller.
PNG is lossless, so nothing is given up
PNG packs a picture without discarding anything, just as BMP stores it without discarding anything, so the move from one to the other is lossless. Every colour and every pixel survives exactly. The advantage of the new wrapper is size: a BMP stores every pixel raw, and a PNG of the same picture is usually a fraction of the size.
If you need a BMP specifically
If a program insists on BMP and nothing else, this page cannot give you one. Any image editor can save a BMP from the PNG in a moment, at the cost of the size you saved. For almost all uses, though, the PNG is the better file, and you will not miss the BMP.
What is kept
Every pixel and the proportions
When you rotate BMP files this way, every pixel of the picture is kept. Nothing is resized, cropped or stretched, and the shape of the picture simply changes between landscape and portrait. The colours and the detail stay exactly as they were.
The resolution the file records
A picture file records a resolution, the dots per inch it is meant to print at. That note is carried over, so a scan turned upright still prints at the size it did before. This matters for scanned pages, where the physical size is part of the meaning: an A4 page scanned sideways and rotated upright is still A4.
Why this matters for old scans
Scans stored as BMP often carry their resolution in the header. By carrying it across to the PNG, the rotated picture keeps its intended physical size, so it fits a page properly when you place it in a document or send it to a printer.
What a BMP file is, and why it is so big
BMP, short for bitmap, is one of the oldest picture formats in everyday use. It stores a short header, which says how large the picture is and how many dots per inch it should print at, followed by the colour of every pixel in order, with no compression whatsoever. That simplicity made it easy for early software to read and write, and it is why BMP still turns up in old scanners, instruments, legacy programs and archives. It is also why the files are so heavy: a screen-sized BMP is several megabytes, whatever it shows.
When you rotate a BMP with this page, you also get a bonus. Because the corrected picture is saved as a PNG, which compresses without loss, the file is usually a fraction of the size of the original. A ten-megabyte BMP may become a PNG of one or two megabytes, with every pixel identical. So to rotate BMP files here is also, in effect, to compress them, and to move them into a format that every modern program understands.
Why old equipment still writes BMP
Simple devices and older software favour BMP because it needs almost no code to produce and no licensing. A laboratory instrument, a measuring device or an early scanner can write a bitmap with a few lines of program. The result is a file anyone can read, but one that is rarely stored in the orientation or the size that later users want. That is the origin of most of the sideways BMPs that people end up needing to rotate.
Scanned pages in BMP
Scans are among the most common reasons to rotate BMP files. Older scanner software often offers BMP as a save option, and pages scanned on a flatbed in landscape position end up stored on their side. Once you rotate the BMP, the page reads normally and can go into a document, an email or an archive. Because the resolution recorded in the BMP header is carried across, the page keeps its intended physical size, so an A4 scan is still A4 on paper.
If you have a whole stack of such pages, check how they were scanned: usually they all need the same turn. Rotate BMP files in groups that need the same correction, check one result in each group at full size and then do the rest. When the pages are all upright, you can combine them with the PNG to PDF converter into a single document, with every page the right way up.
Checking that text stays readable
Because both BMP and PNG keep every pixel, the text in a scan is exactly as sharp after rotation as before. If the text looks soft, it was soft in the scan; rotation neither improves nor worsens it. For readability, the thing to check is simply that the page is upright and that the whole page is present.
Instrument and technical images
Laboratory and technical equipment frequently writes BMP images: microscope captures, measurement plots, camera frames from inspection systems. These often come out in an orientation set by the way the device was mounted, which may not match how the results are reported. Rotating them with this page brings the images into line with the report, without any loss of data in the pixels that remain.
For images where exact pixel values matter, such as measurements, remember that the rotation itself does not alter any value. Every pixel is moved, not changed. Keep the original BMP as the record, and use the rotated PNG for reports and sharing.
Documenting what you did
In technical work it is good practice to note that an image was rotated, and by how much. Add a line in your report or a note in the file name, such as the original name plus a suffix for the turn. It takes a few seconds and prevents confusion if someone later compares the picture with the original.
How to rotate BMP files here
Add your picture
Drop the BMP onto the page or pick it from your device. It is read inside your browser and is not uploaded.
Choose the turn
Pick a quarter turn left, a quarter turn right or a half turn. Check the preview to be sure the picture is upright.
Rotate and check
Press the button and download the corrected picture, which arrives as a PNG. Open it and make sure it is upright and that nothing else has changed.
Tips for a clean result
Rotate before other steps
If the picture is going into a document or a layout, rotate the BMP first so everything that follows is upright.
Keep the original
Keep the original BMP in case you need that exact file for a legacy program.
Use the preview
Choose the turn by looking at the preview rather than guessing, and you will get it right first time.
Questions people ask before rotating
Why did I get a PNG instead of a BMP?
Because a browser cannot write BMP. The picture is identical; only the wrapper differs. PNG is lossless and usually much smaller.
Will the quality drop?
No. Both BMP and PNG keep every pixel, so nothing is lost in the move.
Can I rotate by a few degrees?
No. Only whole quarter turns are possible. A slightly crooked picture needs a different tool.
Is my picture uploaded?
No. Everything runs in your browser and the picture never leaves your device.
Who needs to rotate BMP files
People with old scans
Old scanners store pages in odd orientations. Rotating the BMP puts them right.
Users of legacy and technical equipment
Instruments often write images in a fixed orientation that does not match the report. Turning them fixes it.
Anyone tidying an archive
Archives of BMP files often include sideways pictures. A quick turn makes them usable.
Common mistakes
Expecting a BMP back
The result is a PNG. If you need a BMP, keep the original.
Turning the wrong way
Look at the preview, and if it is wrong, start again from the original.
Deleting the original
Keep it, in case a program insists on BMP.
Related tools
Because BMP files are large, compress BMP turns them into much smaller PNGs while lowering the resolution if you wish. For other pictures, rotate PNG, rotate JPG and rotate HEIC work in the same way, and rotate PDF turns document pages. To put pictures into a document, use PNG to PDF, to make a lighter picture, PNG to JPG, and to label one, add a watermark to PNG.
When to rotate BMP files, and when not to
You should rotate BMP files whenever the picture will leave your own devices and has to look right everywhere: an upload form, an email, a document, a website, an archive. It is less necessary if the picture will only be viewed in the program that made it, and it is the wrong tool for a picture that is merely slightly crooked, which needs straightening by degrees. If a program absolutely requires BMP, keep the original and use it for that purpose.
For the common cases, such as old scans, instrument images and archive clean-ups, it is quick, private and lossless to rotate BMP files in the browser. Your original is never changed, so you can come back and rotate a BMP again from the original whenever you like, with a different turn if the first was not right.
Batches of pictures
If you have many pictures to correct, rotate BMP files one at a time and keep the originals in a separate folder. Work through them in groups: all the quarter-turn-left ones, then all the quarter-turn-right ones. Check one result in each group at full size before you do the rest.
Large pictures and slow devices
Everything runs on your own device, so very large pictures depend on its memory. A BMP of a few thousand pixels on a side is no trouble for a modern computer. A very large image may be slow on an older phone. If it struggles, give the browser a moment and avoid switching to other apps while it works.
Making the file smaller afterwards
The PNG you get is already much smaller than the BMP. If it is still too large for where it is going, you can lower the resolution with the PNG compressor, or convert a photograph to JPG for a still lighter file. Doing that after you rotate BMP files means you start from an upright picture and make one decision about size.
Checking the result properly
After you rotate a BMP, open the PNG at the size you will use. Check that it is upright, that small details are still sharp and that nothing has been cut off. If everything looks right, the job is done. If the picture is still wrong, rotate the BMP again from the original with a different choice.
A simple routine to rotate BMP files well
Look at the picture and decide which turn it needs. Rotate the BMP once, using the preview to confirm. Download the PNG and check it at the size you will use. Then send, upload or place it, and keep the original. This routine takes less than a minute, and it works whether you rotate BMP files once a month or every day. If you rotate BMP files in batches, do them in groups that need the same turn, and check one in each group before you continue.
Your picture stays on your device
The rotation happens locally. Your picture is read by your own browser, turned and saved there and handed back. Nothing is uploaded, so there is no copy on a server and no one else who could see it. For scans of documents and instrument images, that is the safe way to rotate BMP files.
A worked example
Say you have a scanned page saved by an old scanner as a BMP of 2480 by 3508 pixels, but it is lying on its side. You drop the BMP here, choose a quarter turn to the left and check the preview. You press the button and download the corrected picture as a PNG: upright, every pixel intact and much smaller than the BMP. The recorded resolution is carried over, so it still prints as A4.
Rotate BMP: a short recap
To rotate a BMP is to fix its orientation for good, with no loss, and to move it into a smaller, friendlier format. When you rotate BMP files with this page, you choose the turn, check the preview and download the result as a PNG. Every time you rotate a BMP, every pixel is kept, so you can rotate BMP pictures as often as you like. If you need to rotate BMP files in bulk, work in groups. And whenever you rotate a BMP that matters, keep the original beside it, in case a legacy program ever asks for exactly that file.
Before you close the page
Check that you downloaded the corrected PNG, that it is upright, and that you kept the original BMP.
Summary
To rotate BMP files here, drop the picture, choose the turn and download the result. Nothing is scaled or cropped, and every pixel and the recorded resolution are kept. The result is a PNG, because a browser cannot write BMP: the picture is identical, the wrapper is not. Only whole quarter turns are possible. Nothing leaves your device.