About the KB to MB
This KB to MB converter turns kilobytes into megabytes — and megabytes back into kilobytes — while also showing the size in bytes and gigabytes. Enter a number, say whether it is in KB or MB, and pick the counting system that matches where the figure came from.
The choice matters because two conventions are in everyday use. Storage makers, network speeds, macOS and most websites use decimal (SI) prefixes, where 1 MB = 1,000 KB = 1,000,000 bytes. Windows File Explorer and many programmers use binary sizes, where 1 "MB" really means 1 MiB = 1,024 KiB = 1,048,576 bytes. The same file can therefore show slightly different sizes depending on which system reports it.
Use it to check whether an image fits an upload limit, to estimate how many attachments fit in an email, or to reconcile the size your operating system shows with the number a website quotes. Both results are shown so you can see the gap at a glance.
With the default inputs, the megabytes is 2.5 MB. Change any value above to recalculate instantly.
How to use the kb to mb
- 1Type the file size.
- 2Choose whether the number is in kilobytes or megabytes.
- 3Pick decimal (1000) or binary (1024) to match where the number came from.
- 4Read megabytes as the main result, plus kilobytes, bytes and gigabytes.
- 5Compare with the "other system" figure if your computer shows a different size.
Formula and method
In the decimal (SI) system each prefix step is a factor of 1,000: 1 KB = 1,000 bytes and 1 MB = 1,000 KB. In the binary (IEC) system each step is 1,024 = 2¹⁰: 1 KiB = 1,024 bytes and 1 MiB = 1,024 KiB = 1,048,576 bytes.
The tool converts your input to bytes using the system you choose, then divides by the base once for kilobytes, twice for megabytes and three times for gigabytes. It also re-expresses the same bytes in the other system so you can compare what different software reports.
- KB / KiB
- Kilobyte (1,000 B) / kibibyte (1,024 B)
- MB / MiB
- Megabyte (1,000,000 B) / mebibyte (1,048,576 B)
- B
- Byte (8 bits)
Worked examples
2,500 KB photo, decimal units
2,500 KB ÷ 1,000 = 2.5 MB, or 2,500,000 bytes. Windows, which divides by 1,024 twice, would show the same file as about 2.38 MB.
2,500 KiB in binary units
2,500 KiB ÷ 1,024 = 2.4414 MiB. In bytes that is 2,500 × 1,024 = 2,560,000 B.
5 MB upload limit in KB
5 MB × 1,000 = 5,000 KB. If the site uses binary units the limit would be 5 × 1,024 = 5,120 KiB instead.
Frequently asked questions
Is 1 MB 1000 KB or 1024 KB?+
Both are used. Under SI (decimal) rules 1 MB = 1,000 KB. Under the binary convention used by Windows and for RAM, 1 MiB = 1,024 KiB. The IEC names KiB and MiB were created to remove the ambiguity.
How do I convert KB to MB?+
Divide kilobytes by 1,000 for decimal megabytes, or by 1,024 for binary mebibytes. For example, 3,000 KB is 3 MB (decimal) or 2.93 MiB (binary).
Why does Windows show a smaller size than the website?+
Windows divides by 1,024 at each step but labels the result "MB". A 10,000,000-byte file is 10 MB in decimal terms but shows as 9.54 MB in Windows.
How many KB is 1 GB?+
In decimal units 1 GB = 1,000,000 KB. In binary units 1 GiB = 1,048,576 KiB.
What is the difference between KB and Kb?+
A capital B means bytes and a lowercase b means bits; 1 byte = 8 bits. Network speeds are usually quoted in kilobits or megabits per second (kbps, Mbps).