Computers & Laptops

Storage Unit Converter

Convert between bits, bytes, kB, MB, GB, TB, PB and their binary counterparts - with both conventions labelled.

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Result

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Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

There are two conventions and they are not the same. A kilobyte is a thousand bytes to a drive manufacturer and 1,024 to an operating system, and the gap compounds with every prefix: 2.4% at the kilobyte, 7.4% at the gigabyte, 9.95% at the terabyte.

This converter shows both families at once and labels every row, so nothing crosses between them without you seeing it.

How to use this calculator

  1. Enter the figure you have.
  2. Pick the unit it is in. The list says which convention each one belongs to.
  3. Pick the unit you want.

All units are shown regardless, so you only need to be sure of what you started with.

The formula

Decimal:  kB = 1,000 B   MB = 1,000 kB   GB = 1,000 MB   TB = 1,000 GB
Binary:   KiB = 1,024 B  MiB = 1,024 KiB  GiB = 1,024 MiB  TiB = 1,024 GiB
Bits:     1 byte = 8 bits

Everything converts through bytes, so no pair of units needs its own factor and no two pairs can disagree.

SymbolMeaningUnit
Value The quantity you have any

Worked example

One terabyte, as sold:

1 TB  = 1,000,000,000,000 bytes
      = 1,000 GB
      = 931.32 GiB
      = 0.909 TiB

Which is why a 1 TB drive appears as 931 GB in Windows. Nothing is missing; the label is using a decimal prefix on a binary count.

Notes and limits

  • Drive manufacturers use decimal units. Windows reports binary units under decimal names, which is where the apparent shortfall comes from. macOS has reported decimal since 10.6, so the same drive reads differently on the two.
  • Memory is the exception: RAM is sold and reported in binary units under decimal names by universal convention, so a "16 GB" module really is 16 GiB.
  • Network speeds are in bits, storage is in bytes, and the factor is eight. That is the transfer time calculator's territory.
  • The IEC names - kibibyte, mebibyte, gibibyte - exist precisely to end this ambiguity, and are worth using where precision matters.

What this calculation assumes

  • Every conversion is exact - these are definitions rather than measurements.
  • Each unit is labelled with the convention it belongs to, and nothing crosses between them silently.

Frequently asked questions

Why does my 1 TB drive show as 931 GB?

Because the drive holds a million million bytes, which is 1 TB in decimal units, and Windows divides by 1,024 three times and still calls the result "GB". Both counts are of the same bytes. macOS shows about 1,000 GB for the same drive.

Is 1 GB 1,000 MB or 1,024 MB?

In decimal units, 1,000. In binary units the equivalent is 1 GiB = 1,024 MiB. The confusion comes from using the decimal name for the binary quantity, which is exactly what the IEC names were introduced to fix.

How many bytes in a gigabyte?

1,000,000,000 in a decimal GB, and 1,073,741,824 in a binary GiB. The difference is 7.4%, and it grows to almost 10% at the terabyte.

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