File Size Converter (Bytes, KB, MB, GB)
Convert between bytes, KB, MB, GB and TB - free, no upload.
What this tool does
Enter an amount and a unit, choose binary or decimal, and every other unit updates instantly, including the exact byte count.
Converts between bytes, KB/KiB, MB/MiB, GB/GiB, TB/TiB and PB/PiB in one step.
Shows every unit's equivalent value at once, not just one conversion at a time.
Lets you switch between the binary (1024) and decimal (1000) convention explicitly.
Shows the exact byte count alongside every unit, so you always have the one figure that doesn't depend on which convention you picked.
Highlights whichever unit you entered the value in, so it's clear which row is your input and which are the converted results.
How to use it
- Enter an amount and choose its unit.
- Choose Binary or Decimal.
- Read off any other unit's equivalent value instantly.
Why use this converter
KB, MB, GB and the binary KiB, MiB, GiB are easy to confuse, and storage sellers and operating systems use different ones. A converter shows every unit at once.
Why we built it
We built the file size converter to keep the binary (1024) and decimal (1000) conventions clearly apart. Convert internet speeds with the data transfer rate converter and check types with the file type checker.
For a neighbouring job there is also the File Joiner and the File Splitter.
For a neighbouring job there is also the Download Time Calculator.
Who this tool is for
- People comparing storage and download sizes
- Developers and IT staff
- Students learning bytes and bits
When to use it
- Comparing storage and download sizes.
- Understanding why a drive shows less space.
- Planning uploads and quotas.
- Programming and sysadmin tasks.
Why a 1GB file and "1 GB" on a drive label don't quite match
Two genuinely different conventions both use the same unit names in everyday use.
Operating systems have historically reported file and drive sizes using powers of 1024 (1 KB = 1024 bytes), while storage manufacturers and network speeds are measured in powers of 1000 (1 KB = 1000 bytes) - both usually just called "KB", which is exactly why a drive labelled 1TB shows up as roughly 931GB in an operating system's binary-based display. This tool keeps the two conventions clearly separate and labelled (KiB/MiB/GiB for binary, KB/MB/GB for decimal) rather than picking one silently.
How the exact byte count is calculated
Every other unit is just the same byte figure divided differently.
Whichever unit and amount you enter, this tool first converts it to a plain byte count by raising the chosen base (1024 or 1000) to the power matching that unit's position - for example, entering 2 in GiB under the binary convention multiplies 2 by 1024 three times over (1024³) to get the byte count. Every other unit shown is then that same byte figure divided back down by the matching power of the same base, so all the values on the page are always different views of one underlying number rather than independently rounded conversions that could drift apart.
| Unit (binary / decimal) | Bytes |
|---|---|
| KiB / KB | base¹ |
| MiB / MB | base² |
| GiB / GB | base³ |
| TiB / TB | base⁴ |
| PiB / PB | base⁵ |
This tool is a pure unit conversion, not a measurement of anything - it doesn't inspect a real file, so it can't account for how a filesystem rounds a file up to its own block size, which is why the number shown here and the size a file manager reports for an actual file on disk can differ slightly even when both are technically correct.
What you give it, and what you get back
| Item | Details |
|---|---|
| Input | A size and unit. |
| Mode | Decimal (1000) or binary (1024). |
| Output | All units from bytes to PB. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Numbers differ from my OS | It uses binary units. | Switch the mode. |
| KB vs KiB confusion | They differ by 2.4%. | Choose the one you need. |
| Compression estimate wanted | This is only units. | Use compression tools. |
Assumptions and limitations
- This is a pure unit conversion - it doesn't estimate compression, deduplication, or actual disk usage for a real file.
Frequently asked questions
How do I convert bytes to MB or GB for free?
Enter the byte amount, choose Binary or Decimal, and every unit's equivalent is shown instantly.
Why does my file manager show a different size than the file's properties in bytes?
Some tools round differently or use the binary versus decimal convention inconsistently - use this tool's exact byte value to check.
What's the difference between KB and KiB?
KB (decimal) is 1000 bytes; KiB (binary) is 1024 bytes - they're often both called "KB" in everyday use, which causes confusion.
Which convention should I use?
Operating systems typically display binary (1024-based); storage manufacturers and network speeds typically use decimal (1000-based) - match whichever source you're comparing against.
Is my data uploaded anywhere?
No. This is a simple calculation done entirely in your browser.
How is the byte count actually calculated?
Your entered amount is converted to bytes by raising the chosen base (1024 for binary, 1000 for decimal) to the power matching your unit's position, then every other unit shown is that same byte figure divided back down - so all the values stay consistent with one underlying number.
Why doesn't this match the size my file manager shows for a real file?
This tool performs a pure unit conversion on the number you type in - it doesn't inspect an actual file, so it can't reflect filesystem block-size rounding, which is a common reason a real file's reported size differs slightly from a plain conversion.