What is Data Size Conversion?
Digital storage and transfer sizes are counted in bytes and their multiples — but there are two competing systems of multiples. The decimal (SI) units go in steps of 1,000: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB). The binary (IEC) units go in steps of 1,024: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), tebibyte (TiB). Storage manufacturers use decimal; operating systems often report binary — which is exactly why a “1 TB” drive shows up as ~931 “GB” in Windows.
What Does This Tool Do?
Enter a size, choose the source and target units — decimal, binary, bytes, or bits — and get the exact conversion instantly, plus a table of the same size in every supported unit. It’s the quickest way to translate between what the box says, what the OS says, and what your code says.
How to Use This Tool
- Type the size value.
- Pick the from and to units (choices are remembered).
- Read the result and the all-units table; copy with one click.
- Use ⇄ to reverse the conversion.
Decimal vs Binary Units
| Decimal (SI) | Size | Binary (IEC) | Size | Difference |
|---|---|---|---|---|
| Kilobyte (KB) | 10³ = 1,000 B | Kibibyte (KiB) | 2¹⁰ = 1,024 B | 2.4% |
| Megabyte (MB) | 10⁶ B | Mebibyte (MiB) | 2²⁰ = 1,048,576 B | 4.9% |
| Gigabyte (GB) | 10⁹ B | Gibibyte (GiB) | 2³⁰ ≈ 1.074×10⁹ B | 7.4% |
| Terabyte (TB) | 10¹² B | Tebibyte (TiB) | 2⁴⁰ ≈ 1.100×10¹² B | 10.0% |
The gap grows with scale — at petabytes it passes 12%. When a cloud bill, a database quota, and a monitoring dashboard disagree about “the same” number, this table is usually the explanation.
The 1 TB Drive Mystery, Solved
A drive sold as 1 TB contains 1,000,000,000,000 bytes — the manufacturer’s decimal claim is true. Windows divides that by 1024³ and displays 931 GB (it computes GiB but labels it “GB”, the historical confusion at the heart of this topic). Nothing was stolen; the two numbers describe the same bytes in different units. macOS switched to true decimal in 2009, so the same drive shows 1 TB there — and Linux tools let you choose (ls -h vs ls --si).
Bits vs Bytes: the Other Trap
Network speeds are quoted in bits per second (Mbps), storage in bytes (MB). One byte is 8 bits, so a 100 Mbps connection downloads at most 12.5 MB/s — protocol overhead makes the real figure a bit lower. When a “500 mega” plan delivers “only” 60 MB/s downloads, it’s delivering exactly what was sold. Lowercase b is bits, uppercase B is bytes; the difference is a factor of 8, which is why the units look annoyingly similar but matter enormously.
Frequently Asked Questions
Is my data private?
Yes — the conversion runs entirely in your browser; nothing is transmitted.
Should I use KB or KiB in my own writing?
If you mean 1,024 bytes, the unambiguous choice is KiB — that’s what the IEC standard is for, and OSs like Ubuntu already use it. In marketing-adjacent or general writing, KB = 1,000 is technically standard (SI), even though decades of usage blur it. The honest rule: use KiB/MiB/GiB whenever the power-of-two meaning matters.
How many photos/songs/videos fit in a gigabyte?
Rough figures: a smartphone photo is 2–5 MB (so ~250–500 per GB), an MP3 song 3–5 MB (~250 per GB), an hour of streaming HD video 1–3 GB, and 4K video 7–20 GB per hour. These vary with compression settings, but they’re good capacity-planning anchors.
Why does my download speed not match my internet plan?
Plans are sold in megabits per second, downloads display in megabytes per second — divide the plan by 8 for the theoretical maximum, then expect ~5–10% less for protocol overhead. A 300 Mbps plan → ~37.5 MB/s ceiling → ~34 MB/s realistic.
Is a "megabyte" 1,000,000 or 1,048,576 bytes?
Officially 1,000,000 (SI). Historically — and still in Windows Explorer and much software — 1,048,576, which the IEC renamed “mebibyte” (MiB) in 1998 to end the ambiguity. This converter offers both as separate units, so you can be precise about which one a number means.