File Size Calculator: Convert Bits, Bytes, KB, MB, GB, TB
Convert between bits, bytes, kilobytes, megabytes, gigabytes, and terabytes in binary (1024) or decimal (1000). Matches how Windows reports size or how vendors label drives. Free, runs in your browser.
What this tool does
Enter a file size and choose the unitโbits, bytes, or any of the larger prefixes (KB through EB). The result appears in every other unit as you type. Switch to binary (1024) when you want the same convention as Windows and most file managers, or decimal (1000) when youโre comparing to storage specs or data caps. The Information Hub below the calculator shows how the conversion is derived and a reference table of common media sizes.
Bits vs bytes
File size is in bytes (and units built on bytes). Speeds are in bits per secondโMbps, Gbps. One byte is 8 bits, so and . Confusing the two is easy: a 100 Mbps link moves 12.5 MB per second, not 100 MB/s.
Binary (1024) vs decimal (1000)
In binary (IEC), each step is 1024: 1 KiB = 1024 B, 1 MiB = 1024 KiB, 1 GiB = 1024 MiB. So 1 GiB = = 1,073,741,824 bytes. In decimal (SI), each step is 1000: 1 KB = 1000 B, 1 MB = 1000 KB, 1 GB = 1000 MB, so 1 GB = = 1,000,000,000 bytes. A drive sold as "1 TB" holds bytes; in Windows (binary) that shows as about 931 GiB. The calculatorโs base toggle lets you match whichever convention youโre working with.
Common file and storage sizes
In the Information Hub under the calculator youโll find a Common media and storage sizes tableโfloppy, CD, DVD, Blu-ray, typical MP3 and videoโas a ballpark. Use the tool to convert any of those into bits, bytes, or another unit. For email, 10โ25 MB is a safe attachment limit on most providers; for anything bigger, share a link from cloud storage instead.
File size limits (file systems)
Maximum file size depends on the file system. FAT32 limits a single file to bytes (4 GB minus 1 byte). NTFS and exFAT support far larger filesโup to 16 EB in current specs. When moving or creating very large files (e.g. video, disk images), make sure the destination volume uses a file system that supports that size.
File Size Calculator FAQ
Why does my 1 TB drive show only about 931 GB in Windows?
Storage makers use decimal units: 1 TB = 1,000,000,000,000 bytes. Windows uses binary: 1 TiB = 1,099,511,627,776 bytes, and it labels it "TB" in the UI. So a drive sold as 1 TB (10ยนยฒ bytes) is 10ยนยฒ รท 1024ยณ โ 931 GiB. You didnโt lose spaceโthe same bytes are there; the units and base (1000 vs 1024) differ.
What is the difference between KB and KiB?
KB (kilobyte) is decimal: 1 KB = 1,000 bytes. KiB (kibibyte) is binary: 1 KiB = 1,024 bytes. Same idea for MB/MiB, GB/GiB, and so on. Windows and many apps still say "KB" and "MB" but use 1024 under the hood, which is why the IEC invented KiB, MiB, GiBโto avoid mixing decimal names with binary math.
How do I convert file size from bits to bytes?
One byte equals 8 bits. Divide bits by 8 to get bytes (e.g. 1,000 bits = 125 bytes). Multiply bytes by 8 to get bits. The tool above shows the same size in every unit so you can read off the value you need.
What file size can I safely send by email?
Most providers cap attachments at 25โ50 MB; 5โ10 MB is a safe bet so the message doesnโt bounce or get stripped. For anything larger, use a link from a file-sharing or cloud service instead of attaching.
Why 1024 instead of 1000 for "kilo" in file sizes?
Computers work in powers of two. 1024 is 2ยนโฐ, so it fits how memory and addressing work. Early on, "kilo" was used for 1024 in computing. Later, standards bodies said "kilo" should mean 1000 (SI) and introduced "kibi" (KiB) for 1024. Thatโs why you see both bases today.
What are typical file sizes for photos, video, and audio?
A 12 MP photo (JPG) is often 3โ5 MB. A 3โminute MP3 is roughly 3โ5 MB; the same as uncompressed WAV is about 30 MB. SD video runs about 1 GB per hour; 1080p often 4โ8 GB per hour. Exact sizes depend on resolution, codec, and quality settings.
How do I reduce file size?
For documents and spreadsheets, avoid embedding huge images; compress images before inserting. For media, use compressed formats (e.g. JPG, MP3, H.264) and lower bitrates or resolution. Archivers (ZIP, 7z) shrink text and some binaries; they rarely shrink already-compressed media.