1,000 KB on the decimal scale used for file sizes, which is 1,000,000 bytes. Software counting in binary units gives 1,024 KB for the same megabyte, though the correct name for that quantity is the mebibyte and its symbol is MiB. When a limit is close, the decimal figure is the safer one to plan against.

How many KB is 0.5 MB?

500 KB, since half a megabyte is half a million bytes. Under the binary convention the same file reads as 488 KiB. That 12 KB gap is invisible in ordinary use and matters only when an upload limit sits between the two figures, which is exactly the situation that sends people to this conversion.

My upload keeps failing even though my file is under the limit. Why?

Usually one of three things: the limit is measured in binary units while your file manager reports decimal, the upload adds encoding overhead that pushes the transmitted size above the stored size, or the limit applies to the whole request rather than the single file. Trimming to about ninety percent of the stated cap clears all three.

Is KB bigger than MB?

No. A megabyte is a thousand times larger than a kilobyte, so any figure in MB becomes a much bigger number when written in KB. The ladder runs byte, kilobyte, megabyte, gigabyte, terabyte, with a factor of a thousand at each step on the decimal scale that storage and file sizes use.

Does zipping a file make it smaller in KB?

Only if the contents are compressible. Text, spreadsheets and uncompressed images shrink substantially. JPEG photographs, MP4 video, MP3 audio and most PDFs are already compressed, so zipping them saves a fraction of a percent and can even add a few bytes of container overhead, which is no help against a tight limit.

Unit ConvertersFree · no sign-up

MB to KB Converter

Convert MB to KB — for upload limits, attachment caps and image sizes.

Updated August 8, 2026

megabytes (MB)

kilobytes

1,000KB

1 MB = 1,000 KB

In short

How many KB are in a MB?

1,000 KB. Multiply megabytes by 1,000 to get kilobytes, so 2 MB is 2,000 KB and 0.5 MB is 500 KB. Software that uses binary units multiplies by 1,024 instead, which makes the same 2 MB come out as 2,048 KB.

When a form imposes a hard limit in KB, assume decimal and leave headroom rather than aiming at the ceiling.

megabytes to kilobytes — quick reference

megabytes (MB)	kilobytes (KB)
0.5 MB	500 KB
1 MB	1,000 KB
2 MB	2,000 KB
5 MB	5,000 KB
10 MB	10,000 KB
25 MB	25,000 KB
50 MB	50,000 KB
100 MB	100,000 KB

Computed from the exact factor — rounded only for display.

The formula, worked line by line

One multiplication by a thousand, which you can do by moving the decimal point three places. The page exists for what surrounds the sum: which thousand the other side of the transaction is using, and how much room to leave when you cannot find out.

“Convert decimally, then aim ten percent under. The first step gets the number right; the second one gets the upload accepted.”

The rule that covers both conventions without needing to know which is in use

It is a deliberately unambitious rule. There is no way to interrogate a form about its arithmetic, and the difference between a 450 KB file and a 499 KB file is invisible to whoever receives it. Spending the margin is cheaper than spending the afternoon.

kilobytes = megabytes x 1,000
bytes = megabytes x 1,000,000
0.2 MB x 1,000 = 200 KB
1 MiB = 1,024 KiB = 1,048,576 bytes
safe target = stated limit x 0.9

Megabytes against kilobytes, with common upload limits marked on the kilobyte scale.

A scanned document against a 200 KB cap

Scan at 300 dpi, colour: 2.4 MB = 2,400 KB
Same scan, greyscale: 0.9 MB = 900 KB
Reduced to 150 dpi: 0.31 MB = 310 KB
Target with margin: 180 KB
Distance still to cover: about 130 KB

The figures depend on the page, so treat the shape rather than the numbers: dropping colour and halving the resolution each remove far more than any unit conversion, and the conversion is only there to tell you when you have arrived.

Reading a limit you were given

A limit written as "2 MB" is decimal in almost every specification that bothers to say. A limit written in bytes — "maximum 2097152" — is binary, and the giveaway is that the number is a power of two. If a cap is a round decimal number it was written by a person; if it is 1048576 or 5242880 it was written by a program.

The prefixes below the megabyte

Downward from one megabyte

1 MB: 1,000 KB = 1,000,000 bytes
1 KB: 1,000 bytes
1 MiB: 1,024 KiB = 1,048,576 bytes
1 KiB: 1,024 bytes
Difference at MB: 48,576 bytes

That last row is the whole argument in one figure. Just under fifty thousand bytes separate a megabyte from a mebibyte, which is roughly the size of a small icon set and entirely invisible unless a limit falls between them.

One further wrinkle worth knowing: file systems allocate space in blocks, so a file occupying 1,000 KB of content can consume slightly more on disk. That is why a folder can report two sizes, "size" and "size on disk". Upload limits measure content, so the size that matters here is the smaller one.

How to use the MB to KB converter

Multiply by a thousand. That is the whole conversion, and it is not why anybody is here. People convert megabytes to kilobytes because something has refused a file, and the refusal was expressed in units they were not working in — a passport upload capped at 240 KB, a form field that wants under 500 KB, a signature image limited to 50 KB.

The trap in those situations is not the arithmetic but the margin. If a limit reads "maximum 500 KB" and your file is 0.5 MB, you are at exactly 500,000 bytes on the decimal scale and exactly at the ceiling. If the server counts kilobytes as 1,024 bytes, its ceiling is 512,000 bytes and you have room. If it counts as you do, one byte of metadata is enough to fail.

1,000

Kilobytes in a megabyte

decimal, the SI prefix

1,024

What binary software uses

properly KiB, not KB

2.4%

The headroom that hides in it

per prefix step

So the working rule is to convert decimally, which is the stricter of the two readings, and then aim below the number rather than at it. Decimal is stricter because it makes your file appear larger relative to the limit: 500,000 bytes reads as 500 KB decimal but only 488 KB binary. Sizing to the decimal figure is safe under either convention.

The other half of the problem is getting the file under the limit at all, and that is where the units stop mattering and the file format takes over. A photograph at 3 MB will not reach 200 KB by any conversion; it needs re-encoding. Knowing that 200 KB is 0.2 MB tells you how far you have to travel, which is the useful part.

Limits people actually meet, in both units

Signature or ID photo field: 50 KB = 0.05 MB
Typical government form upload: 200 KB = 0.2 MB
Common web image budget: 500 KB = 0.5 MB
One megabyte: 1,000 KB
Common mail attachment ceiling: 25,000 KB = 25 MB

These are representative caps rather than measurements of any particular service — the point is the shape. The left column is the unit a limit is written in, the right is the unit your file manager reports, and converting between them is the same times-a-thousand each time.

Go the other way, from KB to MB

When the file manager gives you kilobytes and the limit is written in megabytes, the reverse page runs the same factor and sets both scales out side by side.

Open KB to MB →

Megabytes converted to kilobytes on the decimal scale, with the binary reading alongside so a borderline file can be checked against either.

Megabytes	Kilobytes (decimal)	Same size in KiB
0.05 MB	50 KB	48.83 KiB
0.1 MB	100 KB	97.66 KiB
0.2 MB	200 KB	195.31 KiB
0.5 MB	500 KB	488.28 KiB
1 MB	1,000 KB	976.56 KiB
1.5 MB	1,500 KB	1,464.84 KiB
2 MB	2,000 KB	1,953.13 KiB
5 MB	5,000 KB	4,882.81 KiB
10 MB	10,000 KB	9,765.63 KiB
25 MB	25,000 KB	24,414.06 KiB
100 MB	100,000 KB	97,656.25 KiB

Middle column multiplies by 1,000 per SI. Right column multiplies by 1,024, which is properly the kibibyte, KiB, under IEC 80000-13.

When the limit and your file manager disagree

You will occasionally hit a file that your computer says is 480 KB, that a form says is 492 KB, and that the form then rejects against a 490 KB cap. Nothing is broken. One side divided by 1,000 and the other by 1,024, and the file sat in the narrow band where the two readings fall on opposite sides of the line.

The same file, measured twice

Actual size: 491,520 bytes
Divided by 1,000: 491.52 KB
Divided by 1,024: 480 KB
Against a 490 KB cap: fails decimal, passes binary
The disputed band: 480 to 492 KB

The band is only 2.4 percent wide, so it catches very few files. The ones it does catch are exactly the files somebody has spent twenty minutes compressing to sit just under the limit, which is why this is remembered as a common problem rather than a rare one.

The practical response is the same one as before: size to the decimal figure and leave a margin. Chasing the last two percent of a limit means depending on a convention nobody has told you, and the cost of guessing wrong is a rejected upload rather than a slightly larger file.

What actually changes a file size

Converting units does not change a file. If the number has to come down, something about the file must change, and which lever works depends entirely on what kind of file it is. Images respond to re-encoding and dimensions; documents respond to what has been embedded in them; archives respond to compression only if the contents are compressible.

Reduce image dimensions before reducing image quality
Export a document to PDF rather than attaching the working file
Check the byte count when a limit is close
Re-measure after every change rather than estimating

Don't

Rename an extension and expect the size to change
Zip a JPEG or an MP4 and expect much — both are already compressed
Aim at exactly the stated limit
Assume a KB limit and a KB reading use the same kilobyte

The zip point catches people regularly. Compression works by finding repetition, and formats such as JPEG, PNG, MP4 and PDF have already removed most of it. Archiving them typically saves a fraction of a percent and occasionally adds a few bytes of container overhead, which is not what somebody up against a cap needs.

Every megabytes value, worked out

110 common megabytes figures each get their own page, with the answer, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.

Questions people ask

Sources

Where the constants and formulas on this page come from. Each line names the figure it backs.

In SI the prefix kilo denotes 10^3 and mega denotes 10^6, so a megabyte is 1,000 kilobytes.
The International System of Units (SI) Brochure — Bureau International des Poids et Mesures
Binary multiples of the byte have their own prefixes and symbols, so 1,024 bytes is a kibibyte, KiB, rather than a kilobyte.
Prefixes for binary multiples — National Institute of Standards and Technology
Formats such as JPEG, PNG and MP4 are already compressed, so archiving them again yields little or no reduction in size.
Optimize your images — web.dev, Google

How to Find the Volume of Hollow, Partial, and Composite Solids

A decomposition-first guide to pipes, frustums, domes, and partly filled tanks, with formulas and checks for avoiding geometric and unit errors.

August 12, 2026 · 12 min read

How to Compare Two Data Sets: Center, Spread, and Relative Difference

A practical workflow for deciding whether two sets are comparable, describing their typical values and variation, and reporting differences without overstating them.

August 11, 2026 · 10 min read

Putting JSON in a URL: Validate, Minify, Percent-Encode, or Base64url?

A decision guide for flattening, encoding, checking, and safely transporting JSON in a query string.

August 11, 2026 · 9 min read