MB to KB Converter

Convert megabytes to kilobytes and back, and see both meanings at once: decimal, where 1 MB = 1000 KB, and binary, where 1 MiB = 1024 KiB. The same file size converter also handles bytes and GB, and shows the exact size of any file on your device.

Amount

Unit

1 MB = 1,000 KB

or 976.563 KiB if your system counts 1 KB as 1024 bytes

1 MB in every unit
Kilobytes (decimal)	1,000 KB
Kibibytes (binary)	976.563 KiB
Megabytes (decimal)	1 MB
Mebibytes (binary)	0.953674 MiB
Bytes	1,000,000 B

How big is my file?

Pick any file to see its exact size in bytes, KB and MB. Only the size is read; the file isn't opened or uploaded.

Choose a file

MB to KB: the two answers

There are two systems of units, and both use the letters KB and MB. Decimal (SI) units step by 1000, like metres and kilometres. Binary units step by 1024, because computer memory is built in powers of two; their exact names are KiB and MiB. Both are correct; what matters is which one the place you're uploading to uses.

Common megabyte values in kilobytes
Megabytes	Decimal (KB)	Binary (KiB)
0.1 MB	100 KB	102.4 KiB
0.5 MB	500 KB	512 KiB
1 MB	1,000 KB	1,024 KiB
2 MB	2,000 KB	2,048 KiB
5 MB	5,000 KB	5,120 KiB
10 MB	10,000 KB	10,240 KiB

Which system to use

Hard drives, SSDs, USB sticks and phone storage are sold in decimal units.
Windows File Explorer shows binary sizes but labels them KB and MB.
Upload forms with photo limits, such as “under 50 KB”, usually count 1 KB as 1024 bytes. The image tools on this site count the same way, and round sizes up so a file is never shown smaller than it is.

Getting a file under a KB limit

A converter only changes the numbers, not the file. To shrink a photo to a limit, use resize image to KB for any size, or the one-step pages for 20KB, 50KB, 100KB and 200KB. To reduce the size without a fixed target, use the image compressor.

Frequently asked questions

How many KB are in 1 MB?

1,000 KB in decimal units, which storage makers and the international standard (SI) use. In binary units, 1 MiB is 1,024 KiB; Windows and many upload forms use this binary meaning but still write it as KB and MB.

How do I convert MB to KB?

Multiply by 1,000 for decimal units (2.5 MB = 2,500 KB), or by 1,024 for binary units (2.5 MiB = 2,560 KiB). To go from KB to MB, divide by the same number.

Which one does an upload form mean by “KB”?

Usually 1,024 bytes, because most forms check the file's size in bytes and divide by 1,024. The difference is small for photo limits (50 KB is 51,200 bytes in binary, 50,000 in decimal), so aim a little below the limit to be safe.

Why does my phone show a different file size than my computer?

macOS, iOS and Android usually count in decimal (1 MB = 1,000,000 bytes), while Windows counts in binary (1 MB = 1,048,576 bytes). The same 5,000,000-byte photo shows as 5 MB on a phone and 4.77 MB on Windows.

What are KiB and MiB?

The unambiguous names for binary units, defined by the IEC: a kibibyte (KiB) is 1,024 bytes and a mebibyte (MiB) is 1,024 KiB. They exist precisely because KB and MB were used for both meanings.

How do I reduce a photo from MB to KB?

Converting the units doesn't change the file. To make a 3 MB photo fit a 100 KB limit, the image itself must be compressed or resized; use resize image to KB, which aims for the exact size you enter.