Converting Megabytes to Kilobytes Made Simple

To convert megabytes to kilobytes, multiply by 1,000: 1 MB = 1,000 kB. If you mean the binary units mebibytes and kibibytes, use 1 MiB = 1,024 KiB instead. The unit labels determine which formula to use.

Megabytes, kilobytes, and binary units

The decimal prefixes kilo and mega represent powers of ten. The binary prefixes kibi and mebi represent powers of two. NIST’s reference on binary prefixes explains the IEC naming convention and compares it with SI prefixes.

“KB” is common in software interfaces, but kB is the decimal symbol used here. Some software labels binary measurements as KB or MB, so check the tool’s definition before converting a displayed value. Our MB versus MiB guide explains this labeling confusion in more detail.

The formula: MB to kB

Kilobytes = megabytes × 1,000

For example:

• 5 MB × 1,000 = 5,000 kB
• 10 MB × 1,000 = 10,000 kB
• 0.5 MB × 1,000 = 500 kB

To convert in the other direction, divide by 1,000. A file of 2,500 kB is 2.5 MB.

When to multiply by 1,024

Use 1,024 when converting between the binary units MiB and KiB:

Kibibytes = mebibytes × 1,024

For example, 5 MiB is 5,120 KiB. That is a different quantity from 5 MB, so changing the unit labels without converting the value gives the wrong result.

Converting between decimal and binary units

When crossing between the two systems, convert through bytes:

1. Multiply the starting value by the number of bytes in its unit.
2. Divide by the number of bytes in the destination unit.

For example, 1 MB is 1,000,000 bytes. Dividing by 1,024 gives 976.5625 KiB. In the other direction, 1 MiB is 1,048,576 bytes, or 1,048.576 kB.

This also explains why the same file can have different numerical sizes in two tools without any bytes being lost.

Choosing the right conversion in practice

Before using a calculator or comparing a file with an upload limit, identify what each side means by its units. If a limit is documented in bytes, compare byte counts directly. If the documentation only says “MB,” check whether it uses decimal units or a binary convention.

Keep the units in spreadsheet column headings, reports, and API documentation. A value such as “5,120” is ambiguous on its own; “5,120 KiB” makes the intended quantity clear.

Also distinguish bytes from bits: 1 byte = 8 bits. A network transfer rate in megabits per second is not a file size in megabytes.

Corrected November 1, 2026: an earlier version incorrectly used 1,024 for MB-to-kilobyte conversion. That factor applies to MiB-to-KiB conversion; decimal MB-to-kB conversion uses 1,000.