What this calculator does
Convert kilobytes to megabytes, or back again, to see whether a file fits a size limit. Kilobytes and megabytes come up with small files: documents, email attachments, web images, upload limits on forms. A site may cap attachments at 2 MB while your file manager reports a scan as 1,850 KB, and you need to know whether it fits.
This page uses decimal SI prefixes, the standard metric ones. With these, a kilobyte (kB) is 1,000 bytes and a megabyte (MB) is 1,000,000 bytes, so 1 MB = 1,000 kB exactly. The binary kibibyte (KiB) is 1,024 bytes and the mebibyte (MiB) is 1,048,576 bytes; many programs show those but label them "KB" and "MB".
Where it's used
Why this math matters outside the classroom:
- Email attachments. Office workers check that five 800 kB attachments total 4,000 kB, or 4 MB, before sending.
- Web pages. Web developers add up image sizes in kB to keep a whole page under a few megabytes.
- Upload limits. Job seekers shrink a resume file when a form caps uploads at 2 MB, which is 2,000 kB.
- Moving the decimal. Students practise moving the decimal point three places, so 2,500 kB becomes 2.5 MB.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 5.NBT.A.2. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter a size in kB or MB.
- Choose kB to MB, or MB to kB.
- Read the result. The table lists common sizes in the chosen direction.
What the inputs mean
- Value to convert
- A data size in decimal kilobytes (for kB → MB) or decimal megabytes (for MB → kB).
- Direction
- Which way to convert.
Formula and method
MB = kB ÷ 1,000 kB = MB × 1,000
In the formulas, kB is the size in kilobytes and MB is the size in megabytes. Kilo means 10³ (a thousand) and mega means 10⁶ (a million). So the two units are exactly 1,000 apart, and converting just moves the decimal point three places.
In binary units the step is 1,024: 1 MiB = 1,024 KiB. Using 1,024 with decimal units, or 1,000 with binary ones, introduces an error of about 2.4%.
Worked example
An image is 500 kB. How many megabytes is it?
- Start from the exact definition, 1 MB = 1,000 kB, so divide the kilobytes by 1,000.
- 500 ÷ 1,000 = 0.5.
Result: 500 kB is 0.5 MB.
Understanding the result
Mental shortcut: move the decimal point three places left for kB to MB and three places right for MB to kB. For decimal units this is exact.
If a file manager shows 1,850 "KB" and it means KiB, the file is 1,850 × 1,024 = 1,894,400 bytes, which is 1.8944 MB in decimal units, still under a 2 MB limit.
A famous mixed unit: the "1.44 MB" floppy disk held 1,440 KiB, which is 1,474,560 bytes. That is 1.47 MB in decimal terms or 1.41 MiB in binary terms; the label used neither system consistently.
Assumptions and limitations
- kB and MB are decimal: 1 kB = 1,000 bytes and 1 MB = 1,000,000 bytes.
- Binary units (KiB, MiB) are not converted here; use the data storage converter for them.
- Upload limits sometimes count binary or decimal units without saying which; leave some margin.
Frequently asked questions
How many kB are in 1 MB?
Exactly 1,000 kB in decimal units. In binary units, 1 MiB is 1,024 KiB.
Is it kB or KB?
The SI symbol for kilo is a lowercase k, so kB is the correct symbol for 1,000 bytes. Uppercase KB is widely used informally, sometimes for 1,000 bytes and sometimes for 1,024. The unambiguous binary symbol is KiB.
How much smaller is a KiB-based figure?
1 KiB is 1.024 kB, so a size given in KiB is a smaller number than the same size in kB, by about 2.3%.
How this calculator is checked
Method: SI prefixes: kilo = 10³, mega = 10⁶; IEC binary prefixes (kibi = 2¹⁰, mebi = 2²⁰) described in content only. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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