File Size Converter
Convert KB, MB, GB, TB — SI and binary units instantly
Instantly convert any file size between bytes, kilobytes, megabytes, gigabytes, and terabytes — in both SI (base-10) and binary (base-2) formats. Results update as you type.
Understanding File Size Units
SI vs Binary Prefixes
There are two systems for measuring file sizes. The SI system (used by storage manufacturers and internet providers) uses powers of 1000: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes. The binary system (used by operating systems) uses powers of 1024: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes. This is why a '1 GB' hard drive shows as about 931 GiB in Windows.
Common Use Cases
Hard drives and SSDs are advertised using SI units (GB, TB), but Windows reports capacity in binary units (GiB), which is why a 1 TB drive appears as ~931 GB in File Explorer. Download speeds from internet providers are typically quoted in SI megabytes per second. RAM capacity is always expressed in binary mebibytes (MiB) or gibibytes (GiB) by the OS.
Quick Reference Examples
A 4K video file of 1 GB (SI) equals exactly 1,000 MB or approximately 953.67 MiB. A 8 GiB USB drive holds exactly 8,589,934,592 bytes. A typical MP3 song at 128 kbps for 4 minutes is about 3.9 MB (SI). Knowing both systems helps you avoid confusion when comparing storage specs, cloud quotas, and OS reports.
SI: 1 MB = 1,000,000 bytes; Binary: 1 MiB = 1,048,576 bytes Frequently Asked Questions
Why does my 1 TB hard drive show less space in Windows?
Hard drive makers use SI units where 1 TB = 1,000,000,000,000 bytes. Windows displays capacity in binary units (GiB), so 1 TB = 1,000,000,000,000 ÷ 1,073,741,824 ≈ 931 GiB. The drive is not missing space — it's just a difference in measurement systems.
What is the difference between MB and MiB?
MB (megabyte) is an SI unit equal to 1,000,000 bytes. MiB (mebibyte) is a binary unit equal to 1,048,576 bytes — about 4.9% larger. Software and operating systems often say 'MB' but mean 'MiB', so it helps to know both.
How many bytes are in a gigabyte?
In the SI system, 1 GB = 1,000,000,000 bytes (1 billion). In the binary system, 1 GiB = 1,073,741,824 bytes (about 1.07 billion). Storage devices use the SI definition; most operating systems use the binary definition.
Which units do internet providers use for download speed?
Internet providers typically use SI megabytes (MB/s) or megabits (Mbps). A 100 Mbps connection transfers 12.5 MB per second in SI terms, or about 11.92 MiB per second in binary terms.
How do I convert GB to GiB?
Divide the number of gigabytes by 1.073741824 to get gibibytes. For example, 50 GB ÷ 1.073741824 ≈ 46.57 GiB. You can also enter 50 in this converter, select GB, and read the GiB result card directly.
What is the formula for file size conversion?
First convert your value to bytes: multiply by 1000^n for SI units (KB=1, MB=2, GB=3, TB=4) or by 1024^n for binary units (KiB=1, MiB=2, GiB=3, TiB=4). Then divide the byte total by the target unit's multiplier. Example: 5 MB = 5 × 1,000,000 = 5,000,000 bytes; in GiB that is 5,000,000 ÷ 1,073,741,824 ≈ 0.00466 GiB.