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GB to MB Converter

Convert gigabytes to megabytes, and any of bytes, KB, MB, GB and TB to the others, in decimal (1,000) or binary (1,024) units.

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Drive makers and network speeds use decimal units (1 GB = 1,000,000,000 bytes). Memory and some operating systems use binary units (1 GiB = 1,073,741,824 bytes), often still labeled GB. That is why a 1 TB drive shows about 931 GB in Windows.

Quick Answer

In decimal units, multiply gigabytes by 1,000 to get megabytes: 1 GB is 1,000 MB and 2.5 GB is 2,500 MB. In binary units, multiply by 1,024: 1 GiB is 1,024 MiB. A 1 TB drive holds 1,000,000,000,000 bytes, which is 931 GiB, the figure Windows shows as GB.

Last updated: 11 November 2026 ·How we calculate this: SI and IEC binary prefixes (NIST)

How This GB to MB Converter Works

Phone plans, file sizes, memory cards and hard drives all talk about megabytes, gigabytes and terabytes, but not always with the same meaning. Choose the unit you have and whether you mean decimal (powers of 1,000) or binary (powers of 1,024) units, enter the amount and press Calculate. The converter shows the size in bytes, KB, MB, GB and TB, the same size in the other system, and the number of bits.

Quick explanation: 1 GB = 1,000 MB (decimal) or 1 GiB = 1,024 MiB (binary).

  • GB to MB: multiply by 1,000.
  • MB to GB: divide by 1,000.
  • GiB to MiB: multiply by 1,024.

How to Use the GB to MB Converter

  1. Choose the unit you have.
  2. Choose decimal (1,000) or binary (1,024) units.
  3. Enter the amount.
  4. Press Calculate.
  5. Read the size in every unit, the other system and bits.

Data Size Formulas

  • Decimal (SI): 1 KB = 1,000 B; 1 MB = 1,000 KB; 1 GB = 1,000 MB; 1 TB = 1,000 GB
  • Binary (IEC): 1 KiB = 1,024 B; 1 MiB = 1,024 KiB; 1 GiB = 1,024 MiB; 1 TiB = 1,024 GiB
  • MB from GB: MB = GB × 1,000 (or MiB = GiB × 1,024)
  • Bits: 1 byte = 8 bits
  • GB to GiB: GiB = GB × 109 ÷ 230 = GB × 0.9313

Key Terms

  • Byte (B): 8 bits, enough to store one basic character.
  • Megabyte (MB): 1,000,000 bytes (decimal).
  • Gigabyte (GB): 1,000,000,000 bytes (decimal).
  • Gibibyte (GiB): 1,073,741,824 bytes (binary).
  • Bit (b): a single 0 or 1; network speeds use bits per second.

Worked Example

A new 2 TB external drive shows less space on a Windows computer. How much should it show?

  • 2 TB = 2 × 1012 = 2,000,000,000,000 bytes
  • In binary units: 2 × 1012 ÷ 240 = 1.819 TiB, or 1,863 GiB
  • Windows labels GiB as GB, so it shows about 1,863 GB. No space is missing.

Going the other way, a 750 MB video is 750 ÷ 1,000 = 0.75 GB.

Real-Life Examples

  • Data plans: 5 GB is 5,000 MB.
  • Drives: 1 TB shows as about 931 GB in Windows.
  • Memory: 16 GiB of RAM is 16,384 MiB.
  • Downloads: a 4.7 GB file is 4,700 MB.

GB vs GiB

  • GB (gigabyte): 109 = 1,000,000,000 bytes.
  • GiB (gibibyte): 230 = 1,073,741,824 bytes.
  • Difference: 1 GiB = 1.0737 GB.

GB to MB Chart

1 GB = 1,000 MB = 10^9 bytes; 1 GiB = 2^30 bytes.

GBMBGiBMiB
1 GB1,000 MB0.93 GiB954 MiB
2 GB2,000 MB1.86 GiB1,907 MiB
4 GB4,000 MB3.73 GiB3,815 MiB
8 GB8,000 MB7.45 GiB7,629 MiB
16 GB16,000 MB14.90 GiB15,259 MiB
32 GB32,000 MB29.80 GiB30,518 MiB
64 GB64,000 MB59.60 GiB61,035 MiB
128 GB128,000 MB119.21 GiB122,070 MiB
256 GB256,000 MB238.42 GiB244,141 MiB
500 GB500,000 MB465.66 GiB476,837 MiB
512 GB512,000 MB476.84 GiB488,281 MiB
1000 GB1e+06 MB931.32 GiB953,674 MiB
2000 GB2e+06 MB1,862.65 GiB1,907,349 MiB
4000 GB4e+06 MB3,725.29 GiB3,814,697 MiB

Why There Are Two Kinds of Gigabyte

Computers address memory in powers of two, and 210 = 1,024 is close to 1,000, so early programmers borrowed the metric prefix kilo for 1,024 bytes. As sizes grew the gap grew too: a binary gigabyte is 7.4% bigger than a decimal one and a binary terabyte almost 10% bigger. In 1998 the International Electrotechnical Commission created separate binary prefixes (kibi, mebi, gibi, tebi) with symbols KiB, MiB, GiB and TiB, and NIST and the IEEE recommend using them.

In practice, drive makers, phone carriers and network speeds use decimal units, macOS and Linux file managers mostly do too, while Windows and RAM sizes use binary units with the old GB label. When a number seems too small or too large, check which system it uses. Network speeds are also given in bits per second, not bytes: a 100 Mbps connection moves at most 12.5 MB per second.

Common Mistakes to Avoid

  • Mixing decimal and binary. 1 GB is 1,000 MB, but 1 GiB is 1,024 MiB.
  • Thinking a drive is short. Windows shows binary GiB labeled GB.
  • Confusing bits and bytes. 100 Mbps is 12.5 MB/s.
  • Using 1,024 for data plans. Carriers use 1,000.
  • Writing Gb for GB. Lower-case b means bits.

Frequently Asked Questions

1,000 MB in decimal units, or 1,024 MiB in a GiB.

Multiply by 1,000 (decimal) or 1,024 (binary).

1,000 MB is 1 GB.

2 GB is 2,000 MB (or 2,048 MiB in 2 GiB).

1,000 GB in a TB, or 1,024 GiB in a TiB.

Windows counts in binary GiB but labels them GB.

Only in binary units (GiB and MiB); in decimal it is 1,000 MB.

1.5 GB is 1,500 MB.

1,000,000,000 bytes, or 1,073,741,824 in a GiB.

References & Sources

SourceUsed ForLink
NIST, Prefixes for binary multiples IEC binary prefixes kibi, mebi, gibi, tebi; 1 GB = 10^9 B and 1 GiB = 2^30 B. https://physics.nist.gov/cuu/Units/binary.html
NIST, Metric (SI) Prefixes kilo, mega, giga and tera as powers of 1,000. https://www.nist.gov/pml/owm/metric-si-prefixes