Convert bytes, kilobytes, mebibytes, and bits

Each unit has an exact factor to the bit: 1 byte = 8 bits, 1 kB = 8 × 10³ bits, 1 KiB = 8 × 1,024 bits. The conversion multiplies then divides, and never treats 1 kB as 1 KiB. That confusion is exactly why a drive sold as “1 TB” appears as roughly 931 GiB in an operating system.

b = x × kfrom ; y = b / kto

1 KiB = 1024 bytes ; 1 kB = 1000 bytes

1 TB = 10¹² bytes ≈ 0.909 TiB

IEC 80000-13 reserves kilo, mega and giga for powers of ten, and introduces kibi, mebi and gibi for powers of 1,024. Drive manufacturers use decimal prefixes; many operating systems display powers of 1,024, sometimes still labelled “GB”. Here the label always matches the factor actually applied.

Value

The quantity alone. The unit is chosen in the From and To lists.

From

Starting unit. Check whether your source means decimal (kB) or binary (KiB).

To

Target unit. The default compares a decimal gigabyte with a binary gibibyte.

Assumptions

• 1 byte = 8 bits.
• The prefixes kB, MB, GB, TB are decimal (10³, 10⁶, 10⁹, 10¹²).
• The prefixes KiB, MiB, GiB, TiB are binary (1,024ⁿ).

Limits

• No machine word, disk sector or filesystem block size.
• Connection throughput is measured in bits per second: convert with the bit unit, then divide by the duration.
• Compression and formatting change the usable space.

A “1 TB” drive really does hold 10¹² bytes: the manufacturer is not cheating. It is the file explorer that divides by 1,024³ while still printing “GB”. For a mobile data plan, a “GB” is almost always decimal. For RAM, by contrast, sizes are binary by construction.

• Treating 1 GB and 1 GiB as the same.

  1 GiB ≈ 1.074 GB, and the gap grows with every prefix.

• Confusing bytes (B) with bits (b).

  A 100 Mb/s link delivers 12.5 MB/s, not 100 MB/s.

• Expecting exactly 1,000 GB on a formatted 1 TB drive.

  Formatting reserves space, and the display often uses powers of 1,024.

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Written by Rédaction HexaCalc (editorial team). Content last updated: August 25, 2026. No third-party medical or financial review is claimed.

• NIST Guide to the SI, Appendix B: Conversion Factors — National Institute of Standards and Technology
• The International System of Units (SI) — Bureau international des poids et mesures (BIPM)