CodeKitHubWhat Is This Tool?
Digital storage is measured in bytes and its multiples: kilobyte (KB), megabyte (MB), gigabyte (GB) and terabyte (TB). The catch is that there are two competing definitions of each step: the decimal standard (1 KB = 1,000 bytes) used by drive manufacturers and networking, and the binary convention (1 KB = 1,024 bytes) traditionally used by operating systems like Windows.
Strictly, the binary units have their own names — KiB, MiB, GiB, TiB (kibibyte, mebibyte, and so on) — but in practice "GB" gets used for both, which is exactly why a 1 TB (decimal) drive appears as roughly 931 GB (binary) in Windows. Nothing is missing; the same bytes are just divided by 1,024 instead of 1,000.
Why Use It?
- Converts across five units at once: bytes, KB, MB, GB and TB — type in any field and all others update.
- Decimal/binary switch: see values in the 1000 base (drive labels, mobile data plans) or the 1024 base (Windows file sizes) and understand why they differ.
- Real-world size chart: photos, songs, movies, USB sticks and hard drives for instant intuition.
- Handles big numbers cleanly, with grouping so 1,073,741,824 bytes stays readable.
- Free, private, works on your phone: everything runs in your browser, nothing is uploaded.
How to Use
- Type a value in any field — bytes, KB, MB, GB or TB — and the other four update instantly.
- Use the base switch to flip between decimal (×1000) and binary (×1024) conversion.
- Check the chart below for typical file and device sizes.
- To decode a drive label, enter its advertised size in decimal, then switch to binary to see what your OS will report.
Example
Input
1 TB drive (decimal, as advertised)Output
≈ 931.32 GB as reported by Windows (binary)1 TB = 1,000,000,000,000 bytes. Divide by 1,024 three times (to KiB, MiB, GiB) and you get ≈ 931.32 — same bytes, different base.
Typical file and storage sizes
| Item | Typical size |
|---|---|
| Plain text email | 20 KB |
| Smartphone photo | 3–5 MB |
| MP3 song (4 min) | 8–10 MB |
| 1 hour of music streaming | 50–150 MB |
| HD movie (1080p) | 4–8 GB |
| 4K movie | 15–30 GB |
| USB stick | 32–256 GB |
| SSD in a laptop | 256 GB–2 TB |
| External hard drive | 1–8 TB |
Decimal vs binary units at a glance
| Unit | Decimal (SI) | Binary (IEC) |
|---|---|---|
| 1 KB / KiB | 1,000 bytes | 1,024 bytes |
| 1 MB / MiB | 1,000,000 bytes | 1,048,576 bytes |
| 1 GB / GiB | 10⁹ bytes | 1,073,741,824 bytes |
| 1 TB / TiB | 10¹² bytes | 1,099,511,627,776 bytes |
Where this fits in real workflows
This conversion decides practical questions daily: whether 500 photos fit on a 2 GB data plan upload, how many 4 GB movies a 256 GB SSD really holds after the decimal/binary haircut, and why a download shows 1.2 GB in the browser but 1.11 GB on disk. When files are too big, compressing them is usually the next step.
For shrinking the actual files rather than converting their units, the image and GIF compressors reduce megabytes directly in your browser.
Frequently Asked Questions
How many MB in a GB?
1 GB = 1,000 MB in the decimal system used by storage manufacturers and mobile data plans, or 1,024 MB in the binary system traditionally used by operating systems. Likewise 1 MB = 1,000 KB (or 1,024), and 1 TB = 1,000 GB (or 1,024). This converter lets you switch between both bases.
Why does my 1 TB drive show only 931 GB?
The manufacturer counts in decimal (1 TB = 10¹² bytes) while Windows divides by 1,024 steps (binary). 10¹² bytes ÷ 1,024³ ≈ 931 GiB, which Windows labels "GB". No space is missing — the same number of bytes is described in two different bases.
What is the difference between GB and GiB?
GB (gigabyte) officially means 10⁹ = 1,000,000,000 bytes; GiB (gibibyte) means 2³⁰ = 1,073,741,824 bytes. The "-bi-" units (KiB, MiB, GiB, TiB) were introduced to end the ambiguity, but everyday software still often writes "GB" while calculating in GiB.
Which base should I use — 1000 or 1024?
Use decimal (1000) for drive labels, mobile data plans, and network speeds; use binary (1024) when matching what Windows reports for files and disks. macOS and most Linux tools now report in decimal, so the same file can legitimately show different "sizes" on different systems.
Is my data stored anywhere?
No. The conversion runs in your browser with JavaScript; nothing you type is sent to a server, stored or logged.