Data storage converter

Convert between bytes, decimal units (KB, MB, GB, TB) and binary units (KiB, MiB, GiB, TiB).

By the Calcist team · Checked against known answers · Updated October 27, 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Next: Working in binary or hex? Use the programmer calculator. Planning a network? Try the subnet calculator.

What it does

This converts between bytes and the two families of storage units: decimal (KB, MB, GB, TB) and binary (KiB, MiB, GiB, TiB). It also answers a very common question: why a new "1 TB" drive shows up as about 931 GB on a computer.

How it's calculated

Decimal units use the SI prefixes, as NIST defines them: kilo = 10³, mega = 10⁶, giga = 10⁹, tera = 10¹². Binary units use the IEC prefixes adopted in 1998: kibi = 2¹⁰, mebi = 2²⁰, gibi = 2³⁰, tebi = 2⁴⁰.

1 KB = 1,000 bytes · 1 MB = 1,000,000 · 1 GB = 1,000,000,000 · 1 TB = 10¹²
1 KiB = 1,024 bytes · 1 MiB = 1,048,576 · 1 GiB = 1,073,741,824 · 1 TiB = 2⁴⁰ = 1,099,511,627,776

To convert, multiply by the first unit's size in bytes and divide by the second's. A byte is 8 bits.

Why does my 1 TB drive show 931 GB?

Storage makers measure capacity in decimal units, so a 1 TB drive holds 1,000,000,000,000 bytes. Some operating systems and apps count in binary units but still label them "GB". Divide by 1,073,741,824 bytes per GiB:

10¹² ÷ 2³⁰ = 931.32 GiB

No space is missing. It's the same number of bytes in a different unit. The formatted file system takes a little more, so the free space you see on a new drive is slightly lower still.

Advertised	Bytes	In binary GB (GiB)	In binary TB (TiB)
128 GB	128,000,000,000	119.21 GiB	0.12 TiB
256 GB	256,000,000,000	238.42 GiB	0.23 TiB
500 GB	500,000,000,000	465.66 GiB	0.45 TiB
1 TB	1,000,000,000,000	931.32 GiB	0.91 TiB
2 TB	2,000,000,000,000	1,862.65 GiB	1.82 TiB
4 TB	4,000,000,000,000	3,725.29 GiB	3.64 TiB

Worked example

A 500 GB SSD is 500 × 10⁹ = 500,000,000,000 bytes. 500,000,000,000 ÷ 1,073,741,824 = 465.66 GiB. The gap grows with each prefix: about 2.4% for kilo vs. kibi, 4.9% for mega, 7.4% for giga and 9.95% for tera.

Limitations

"MB" is sometimes used for 1,048,576 bytes, especially for memory (RAM) and in older software. When the meaning matters, the binary prefixes remove the doubt.
Network and internet speeds use bits per second (Mbps), not bytes. Divide by 8 to get bytes.
Results with more than 15 significant digits are rounded.

Sources

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

1 TB = 10¹² ÷ 2³⁰ = 931.32 GiB ✓
500 GB = 465.66 GiB ✓
1 GiB = 1,073,741,824 bytes ✓
1 MiB = 1.048576 MB ✓
Edge: 8 bits = 1 byte ✓
Edge: a negative amount is rejected ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

Add this calculator to your website (free)

Paste this code into any web page. The calculator works on your page, resizes itself, has no ads and no tracking, and nothing your visitors type is sent anywhere. More about embedding.

<iframe src="https://calcist.com/embed/data-storage-converter/" title="Data storage converter" width="100%" height="640" loading="lazy" style="border:0;max-width:760px"></iframe>
<p style="font:14px/1.4 sans-serif;margin:4px 0 0"><a href="https://calcist.com/data-storage-converter/">Data storage converter</a> by Calcist</p>
<script src="https://calcist.com/embed.js" async></script>

Questions people ask

Is 1 GB 1000 MB or 1024 MB?

By the SI and IEC definitions, 1 GB = 1,000 MB. 1,024 is the binary step: 1 GiB = 1,024 MiB. Some software still uses GB to mean GiB.

How many GB are in a TB?

1,000 GB in 1 TB. In binary units, 1 TiB = 1,024 GiB, and a decimal 1 TB is 931.32 GiB.

What is the difference between GB and GiB?

A GB is 1,000,000,000 bytes. A GiB is 2³⁰ = 1,073,741,824 bytes, about 7.4% bigger.

Why is my hard drive smaller than advertised?

The box uses decimal units (1 TB = 10¹² bytes), and many computers report binary units labeled GB. 10¹² bytes is 931.32 GiB. The file system also takes a little space.

Related calculators

Programmer calculatorBinary, hex, octal and decimal, bitwise math and two's complement.Unit converterLength, weight, volume, temperature, speed, data and more.Scientific notation calculatorConvert to scientific, E and engineering notation, and do math in it.Subnet calculatorIPv4 network, broadcast address, host range and wildcard mask.