Byte Size Converter (KB / KiB / MB / MiB / ...)
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There are two conflicting standards for byte units. SI/decimal: 1 KB = 1000 B, 1 MB = 1 000 000 B. IEC/binary: 1 KiB = 1024 B, 1 MiB = 1 048 576 B. Disk manufacturers use decimal. RAM and most OSes use binary but often label it with the SI prefix (Windows showing 'GB' that's really GiB). This calculator shows both side-by-side so you don't have to guess which one your tool means. Also includes bits for network bandwidth conversions.
Total bytes
1,000,000,000 B
Bits: 8,000,000,000 bit
Decimal (SI, ×1000)
1 KB = 1000 B
- B1,000,000,000
- KB1,000,000
- MB1000
- GB1
- TB0.001
- PB1.0000e-6
Binary (IEC, ×1024)
1 KiB = 1024 B
- B1,000,000,000
- KiB976562.5
- MiB953.6743
- GiB0.931323
- TiB0.000909
- PiB8.8818e-7
Disks use decimal (1 TB = 10¹² B). RAM and most OSes use binary (1 GB = 2³⁰ B, technically 1 GiB). Storage marketing prefers decimal — bigger numbers.
How to use
- Enter a value and pick its unit.
- Read both columns: SI (decimal, ÷1000) on the left, IEC (binary, ÷1024) on the right.
- Bits = bytes × 8. Network speed (Mbps, Gbps) is in bits per second.
Frequently asked questions
- Why two systems?
- Computer science uses powers of 2 because hardware aligns on binary boundaries (RAM chips, page sizes). Marketing and storage default to powers of 10 because it makes drives look bigger ('1 TB' = 0.909 TiB). IEC introduced KiB/MiB/etc in 1998 to disambiguate.
- Why does my 1 TB drive show 931 GB in Windows?
- The drive really is 10¹² bytes (decimal TB). Windows displays it as binary GB (=GiB) without the 'i'. 10¹² / 2³⁰ ≈ 931 GiB. Nothing is missing.
- Are Mbps and MB/s the same?
- No — Mbps is megabits per second (millions of bits, base 10), MB/s is megabytes per second. 1 byte = 8 bits, so 100 Mbps ≈ 12.5 MB/s. Network speeds use bits; file sizes use bytes.
- Which unit should I use in docs?
- Be explicit: 'KiB' if you mean 1024, 'KB' if you mean 1000. If reusing 'KB' for 1024 (the old convention), say so once. Don't write 'KB' and let readers guess.
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