File Size Converter
Convert between bytes, KB, MB, GB, TB, PB and KiB, MiB, GiB, TiB, PiB instantly. See why a "1 TB" drive shows up as 931 GiB, and what your data really weighs.
Finding This File Size Converter Useful?
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Get the Standalone VersionWhat Is a File Size Converter?
A File Size Converter turns a quantity of data from one unit of measurement into another — bytes into kilobytes, megabytes into gigabytes, or the binary equivalents. The tricky part is that there are two systems in common use: SI (decimal, powers of 1000), where 1 kB = 1000 bytes, and IEC (binary, powers of 1024), where 1 KiB = 1024 bytes. Hard drive manufacturers use SI; many operating systems use IEC values but display them with SI symbols. This tool converts between all of them at once, so the confusion disappears.
Key Features
Both Systems Side by Side
SI (kB, MB, GB) and IEC (KiB, MiB, GiB) are shown together, so you can see exactly where the "lost capacity" goes.
Wide Range
From a single bit up to petabytes — and back. Every common file size unit is included.
Copy Any Value
Each result has a copy button. Copy all as a text block for pasting into notes, tickets or documentation.
Live Byte Stats
See the raw byte and bit count, the byte count in hexadecimal, and the SI-to-IEC ratio for GB/GiB.
Quick Presets
One-click buttons for 1 kB, 1 MB, 1 GB, 1 KiB, a CD (700 MB), a DVD (4.7 GB) and more.
Nothing Leaves Your Browser
No server, no analytics, no logging. Conversion runs entirely in JavaScript on your device.
How to Use the File Size Converter
- Enter a value — type a number, or click one of the preset buttons.
- Choose the source unit — from the grouped list. Bits, SI bytes and IEC bytes are separated.
- Pick a display filter — both systems, SI only, or IEC only.
- Read the results — every unit is shown with its converted value, and the highlighted comparison box shows the SI-vs-IEC relationship.
- Copy what you need — use the copy button on any result, or Copy all values for the whole set.
Practical Use Cases
Understanding Drive Capacity
See why a "500 GB" drive shows 465 GiB in your file manager — the manufacturer counts 500 billion bytes, the OS reports 500 ÷ 1.024³ GiB.
Media File Sizes
Compare a 4.7 GB DVD to streaming file sizes and understand compression ratios.
Cloud Storage Costs
Convert between units before estimating how much data you are storing and paying for.
Network Speeds
Convert between bits per second and bytes per second — a "100 Mbps" line delivers about 12.5 MB/s.
Data Analysis
Normalise datasets measured in different units before plotting or comparing.
Learning Units
Understand the difference between MB and MiB, and when each one is the correct choice.
Important Notes and Limitations
A few honest caveats:
• Above about 9 petabytes, precision is limited. JavaScript numbers are IEEE-754 doubles, and integers above 253 (roughly 9×1015) cannot be represented exactly. The tool shows a warning when you cross that threshold. Values below 9 PB are exact for whole-byte inputs.
• Only integer and decimal values are supported. Fractional results (like 1 GB = 0.0009765625 TiB) are shown with rounded decimals, not as exact fractions. For engineering work requiring exact ratios, use a spreadsheet with rational arithmetic.
• Prefixes are case-sensitive. MB is a megabyte (106 bytes), Mb is a megabit (106 bits), and MiB is a mebibyte (220 bytes). The dropdown lists them exactly as the standard defines them.
• This is a unit converter, not a file inspector. It does not read your disk or scan files — it converts numbers you provide. If you need the actual size of a file, use your operating system's file properties dialog.
• Storage device capacities are rarely exactly what the label says. A "1 TB" drive typically contains slightly more than 1012 bytes, but the exact figure varies by manufacturer. The tool converts what you give it; it does not know the exact size of any particular device.
Frequently Asked Questions
Because the manufacturer and the operating system are using different definitions. The manufacturer measures in SI units: 1 TB = 10004 bytes = 1,000,000,000,000 bytes. Your file manager divides that by 10243 = 1,073,741,824 (a GiB) and displays the result as "GB", which comes out to about 931. The drive holds 1012 bytes either way. The tool shows both interpretations of the same byte count so you can see exactly where the discrepancy comes from.
MB (megabyte) is a decimal unit defined as 106 = 1,000,000 bytes. MiB (mebibyte) is a binary unit defined as 220 = 1,048,576 bytes. The two differ by about 4.9%. The IEC introduced the KiB, MiB, GiB family in 1998 to remove ambiguity, but adoption has been inconsistent — many tools still write "MB" when they mean "MiB". This converter shows both so you can match whichever convention your data uses.
A byte is bigger. One byte contains 8 bits. Bits are used for network speeds (Mbps), bytes for storage sizes (MB). That is why a 100 Mbps connection delivers only about 12.5 MB per second — divide by 8. The tool converts between both, so you can move back and forth without remembering the factor.
For whole-byte inputs below 9 petabytes (about 9×1015 bytes), every displayed value is exact to the precision shown — the only rounding is in the final formatting of decimals. Above that threshold, JavaScript cannot represent every integer exactly, and the tool displays a warning. For everyday file sizes, everything is accurate.
No. The whole tool runs in JavaScript in your browser. There is no network request, no analytics, and no logging. You can verify this by opening your browser's network panel while using the tool — nothing is sent. The standalone edition works completely offline.
About the Author — GenieDevs
Get the Standalone Version
File Size Converter — Standalone Edition
One self-contained HTML file with the full converter inside. Keep it on your machine, run it from a USB stick, or use it on an air-gapped computer — no internet connection needed.
Final Takeaway
File size units are one of those small details that cause disproportionate confusion, because two systems with almost the same names coexist — one based on 1000, one on 1024. This tool removes the ambiguity by showing every conversion in both systems at once. Type any value, pick a unit, and see exactly how the same number of bytes reads under SI and IEC conventions. It is accurate for every practical file size, it runs entirely in your browser, and it never sends a byte over the network.