Instant data size conversion — binary (IEC) and decimal (SI) standards
Byte and Bit Converter converts between digital storage units: bits, bytes, kilobytes, megabytes, gigabytes, terabytes, kibibytes, mebibytes, gibibytes, and tebibytes. It handles both SI units (1 KB = 1000 bytes) and IEC binary units (1 KiB = 1024 bytes), and converts network bandwidth between bits/second, kilobits/second, megabits/second, and gigabits/second.
There are two unit systems for digital storage. SI (decimal, metric) units use powers of 10: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes. This is used by hard drive manufacturers, ISPs quoting bandwidth, and SI standards. IEC (binary) units use powers of 2: 1 KiB = 1,024 bytes, 1 GiB = 1,073,741,824 bytes. Operating systems (Windows, macOS, Linux) use binary units internally. The confusion between GB and GiB is why a '1 TB' hard drive shows as '931 GB' in Windows.
Network bandwidth is measured in bits per second (bps). A 100 Mbps connection transfers 100,000,000 bits per second = 12,500,000 bytes per second ≈ 11.9 MiB/s. Download speed calculators often confuse megabits (Mbps, what ISPs advertise) with megabytes (MB/s, what file transfer speeds show). 100 Mbps ÷ 8 = 12.5 MB/s (assuming no overhead).
1 TB hard drive in Windows
Result: 1 TB (SI) = 1,000,000,000,000 bytes ÷ 1,073,741,824 = 931.3 GiB → shown as '931 GB' in Windows
100 Mbps download speed
Result: 100 Mbps = 100,000,000 bits/s ÷ 8 = 12,500,000 bytes/s = 12.5 MB/s = 11.92 MiB/s
Time to transfer 4K movie (50 GB)
Result: 50 GB ÷ 12.5 MB/s = 4,000 seconds ≈ 66.7 minutes on 100 Mbps connection
Why does Windows show less storage than advertised?
Hard drive makers use SI units (1 GB = 1,000,000,000 bytes) for marketing. Windows uses binary units and mislabels them as GB: it shows gibibytes (1 GiB = 1,073,741,824 bytes) but calls them GB. A '1 TB' drive contains exactly 1,000,000,000,000 bytes ÷ 1,073,741,824 = 931.3 GiB, which Windows displays as '931 GB'. macOS switched to reporting decimal GB in 2012, so a '1 TB' drive shows as '1 TB' on Mac.
What is the difference between Mbps and MB/s?
Mbps (megabits per second) measures data transfer rate in bits. MB/s (megabytes per second) measures in bytes. Since 1 byte = 8 bits: 100 Mbps ÷ 8 = 12.5 MB/s. ISPs advertise speeds in Mbps; download progress bars show MB/s. A 100 Mbps plan delivers roughly 12-13 MB/s (slightly less due to protocol overhead from TCP/IP headers, approximately 3-5% overhead).
How much data does streaming video use?
It depends on quality: Netflix SD uses ~1 GB/hour (2.2 Mbps), HD uses ~3 GB/hour (6.7 Mbps), 4K Ultra HD uses ~7 GB/hour (15.6 Mbps). YouTube 1080p60: ~2.5 GB/hour. These rates require a consistent downstream bandwidth of 2-3× the bitrate to avoid buffering. A 25 Mbps connection comfortably handles 4K streaming.
What storage unit should I use in my application?
Depends on your audience. For end users: use the same unit the operating system uses (GB on macOS, GiB displayed as GB on Windows, GiB on Linux). For technical users and server contexts: use MiB/GiB/TiB to be unambiguous. For file sizes in code: use bytes (no unit confusion). The IEC 80000-13 standard recommends always using the KiB/MiB/GiB notation to avoid confusion, though this is rarely done in consumer software.
How much storage does a typical photo, video, or document take?
JPEG photo (12MP, quality 85%): 2-5 MB. RAW photo (12MP): 20-35 MB. 1-minute 1080p30 video (H.264): 150-500 MB. 1-minute 4K30 video (H.264): 400 MB - 2 GB. PDF document (10 pages, images): 1-5 MB. Microsoft Word document (50 pages, no images): 50-100 KB. These are rough ranges — compression settings and content complexity vary widely.