Data Size Converter

How to use it

Type a number and a unit into Size, such as 1.5 GB, 700 MiB or 8 Gb, or press one of the chips under it. Spelled-out units like 5 gigabytes work too. The answer reads 1.5 GB is 1,500,000,000 bytes, and Copy bytes copies the byte count.

The table gives the size in every unit, in three groups: decimal bytes, binary bytes and bits, with the unit you typed highlighted. A note underneath compares the two systems at that size.

To time a transfer, type a rate into Speed, for the transfer time, such as 100 Mbps or 50 MB/s. The answer gives the time in its two largest units, then the seconds and the bits per second.

Examples

1 TB in binary units:

GiB   931.322574615478515625
TiB   0.909494701772928238

The GiB value is exact; the TiB one runs to 28 digits, so it’s rounded to 18.

700 MiB is 734,003,200 bytes, or 734.0032 MB.

4.7 GB with Speed 300 Mbps:

At 300 Mbps that takes 2 minutes 5 seconds
125.333333333333333 seconds at 300,000,000 bits per second.

A decimal comma, as in 1,5 GB, is rejected with "1,5" has a comma that doesn't separate thousands. Write decimals with a point, like 1.5.

Good to know

• SI prefixes count by 1,000 and IEC prefixes by 1,024. A kB is 1,000 bytes and a KiB, a kibibyte as IEC 80000-13 names it, is 1,024. The gap grows with each step: 2.4% at kilo, 7.37% at giga, 12.59% at peta.
• Case matters: B is a byte and b is a bit. 100 Mb is 12.5 MB. Typed all in lowercase, mb or kib in Size reads as bytes. In Speed a lowercase b always means bits, as in networking, so 100 mbps is megabits.
• KB reads as 1,000 bytes. Windows and many memory specs use KB, MB and GB for 1,024-based amounts. Use KiB when that’s what you mean.
• Every value is exact arithmetic, not floating point. A result is written in full up to 24 significant digits, and anything longer is rounded to 18.
• The transfer time is just size divided by speed. Protocol overhead and latency aren’t counted, so a real download takes longer.
• Commas only separate thousands, as in 1,500,000 B. Spaces and underscores are ignored. Each field holds 64 characters, and units go up to peta.

Questions

How many MB are in a GB?

1,000: a gigabyte is 1,000 megabytes, or 1,000,000,000 bytes. With binary units it’s 1,024: a GiB is 1,024 MiB, or 1,073,741,824 bytes.

What’s the difference between GB and GiB?

A GB is 10^9 bytes and a GiB is 2^30, about 7.37% more. Drive makers use the decimal units; memory and many operating systems use the binary ones, often labeled GB.

Why does my 1 TB drive show up as 931 GB?

The drive holds 1,000,000,000,000 bytes, and Windows divides by 1,024 three times but still writes GB, which gives 931.32. macOS has counted in thousands since 10.6, so there the same drive shows as 1 TB.

How long does it take to download 1 GB at 100 Mbps?

80 seconds at best: 1 GB is 8,000,000,000 bits, and 100 Mbps moves 100,000,000 bits a second. Speeds are quoted in bits and files in bytes, so divide by 8 for MB/s: 100 Mbps is 12.5 MB/s.