How much smaller will my BMP get?

For photos and colour scans, commonly ten to twenty times smaller at quality 92, and more if you lower the slider. Pages with lots of empty paper shrink the most. Both sizes are shown when the conversion finishes, so you see the real figure for your file.

Will converting lose quality?

JPG is lossy, so a few pixels change, but at 92 the difference is very hard to spot on photos and scans. Fine black text on white can show faint fringes; keep such pages as PNG if that bothers you.

Can I convert BMP to JPG on Windows 10 or 11 without a website?

Yes. Open the file in Paint, choose Save as and pick JPEG. On a Mac, open it in Preview and use File, then Export, with JPEG as the format. This page is handy on a phone or a computer where you would rather not dig through menus.

Can I convert a whole folder of BMP files at once?

No. This page converts one picture at a time. For a handful of scans that is quick enough; for hundreds, a desktop program with a batch option is the better fit.

The JPG is still too big for the form I am filling in. What now?

Converting keeps every pixel, so a large scan stays fairly large. If the form sets a KB limit, open the compress tool with your BMP instead; it accepts bitmaps directly and reduces the result to the size you enter.

BMP to JPG Converter: Shrink Heavy Bitmap Files

A .bmp file is a bitmap: the colour of every pixel written out one after another, with no compression at all. In the usual 24-bit form that costs three bytes per pixel, so you can predict the size with a calculator. A full-HD screenshot of 1920 × 1080 comes to about 6MB, and an A4 page scanned at 300 DPI (2480 × 3508 pixels) to about 25MB. Paint, scanner software and older Windows programs still hand out files like that, and email attachments and upload boxes choke on them.

JPG keeps the same width and height but describes the picture far more economically, so a photo or colour scan often ends up ten to twenty times lighter. This converter opens the bitmap on your phone or computer and writes that JPG for you.

Before and after

Shelves in a stone alcove stacked with old CRT monitors and open computer cases, photographed in black and white — The picture and its 2400 × 3200 px size stay the same. Only the file changes: BMP at 21.97 MB in, JPG at 1.59 MB out.
JPG drops detail the eye barely notices, which is why the file is 93% smaller.
The numbers are from a real run of the tool above. The pictures here are smaller previews of the actual files.

The same photo saved as JPG — The picture and its 2400 × 3200 px size stay the same. Only the file changes: BMP at 21.97 MB in, JPG at 1.59 MB out.
JPG drops detail the eye barely notices, which is why the file is 93% smaller.
The numbers are from a real run of the tool above. The pictures here are smaller previews of the actual files.

How to use it

Pick the .bmp file. A scan straight from the scanner folder or a picture saved from Paint both work; the file stays on your device the whole time.
Keep the quality at 92 for scans you might print or read closely, or slide it towards 70 if the only goal is a lighter attachment.
Tap Convert and compare the old and new sizes shown under the preview. A 25MB scan dropping to one or two megabytes is typical.
Save the JPG and keep the original bitmap if you still plan to edit the picture.

Why a bitmap is so large, and when it is not

Size in a 24-bit BMP depends only on the pixel count: width × height × 3 bytes, plus a tiny header. A plain white page costs exactly as much as a busy photograph of the same size, which is why a nearly empty scan can still weigh tens of megabytes. JPG spends bytes on detail instead, so empty areas become almost free.

The exception is a black-and-white scan saved as a 1-bit BMP. Each pixel then takes one bit rather than 24, so an A4 text page is closer to 1MB, and converting it to JPG can barely help or even make it bigger, with soft grey fringes around the letters. For text pages, line drawings and diagrams, PNG is usually the better target.

What changes in the JPG

Colours and pixel dimensions stay as they were. A 32-bit bitmap with a see-through background gets a white one, because JPG has no transparency. The print resolution a scanner records in the BMP is not copied over; if a print shop or form asks for a particular DPI, set it afterwards with the DPI tool, which changes only the stored number.

Very large scans, above roughly 16 million pixels (an A4 page at 600 DPI is about 35 million), are scaled down when they are opened so the browser does not run out of memory. The page tells you when this has happened. Scanning at 300 DPI avoids it and is plenty for documents.

Frequently asked questions

How much smaller will my BMP get?: For photos and colour scans, commonly ten to twenty times smaller at quality 92, and more if you lower the slider. Pages with lots of empty paper shrink the most. Both sizes are shown when the conversion finishes, so you see the real figure for your file.
Will converting lose quality?: JPG is lossy, so a few pixels change, but at 92 the difference is very hard to spot on photos and scans. Fine black text on white can show faint fringes; keep such pages as PNG if that bothers you.
Can I convert BMP to JPG on Windows 10 or 11 without a website?: Yes. Open the file in Paint, choose Save as and pick JPEG. On a Mac, open it in Preview and use File, then Export, with JPEG as the format. This page is handy on a phone or a computer where you would rather not dig through menus.
Can I convert a whole folder of BMP files at once?: No. This page converts one picture at a time. For a handful of scans that is quick enough; for hundreds, a desktop program with a batch option is the better fit.
The JPG is still too big for the form I am filling in. What now?: Converting keeps every pixel, so a large scan stays fairly large. If the form sets a KB limit, open the compress tool with your BMP instead; it accepts bitmaps directly and reduces the result to the size you enter.