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Free Data Size Converter Online

Convert between bits, bytes, KB, MB, GB, TB, and PB - shown in both decimal (1000-based) and binary (1024-based) systems at once. Includes a transfer-time estimator and real-world size comparisons.

  • 100% free
  • No signup
  • Runs in your browser
Input is measured in
Unit Decimal (1000) Binary (1024)

Real-world comparison

Your input is roughly equivalent to:

    File transfer time estimator

    Network speeds are measured in bits per second, but file sizes are in bytes - so 1 byte = 8 bits. This estimator accounts for that.

    Quick reference

    • 1 byte = 8 bits
    • 1 KB = 1,000 bytes (decimal) · 1 KiB = 1,024 bytes (binary)
    • 1 MB = 1,000,000 bytes · 1 MiB = 1,048,576 bytes
    • 1 GB = 1,000,000,000 bytes · 1 GiB = 1,073,741,824 bytes
    • 1 TB = 1,000,000,000,000 bytes · 1 TiB = 1,099,511,627,776 bytes

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

    Storage manufacturers use decimal (1000-based) units, while operating systems often display binary (1024-based) units. A “1 TB” drive has 1,000,000,000,000 bytes, but Windows reports this as about 931 GiB because it divides by 1,073,741,824 (1024³) instead of 1,000,000,000,000. Both numbers represent the same physical storage - it’s purely a units convention difference.

    Guide

    Decimal vs. binary: KB vs. KiB

    Data sizes are confusing because two different systems share similar names. In the decimal system, units step up in powers of 1000: 1 kilobyte (KB) = 1000 bytes. In the binary system, they step up in powers of 1024: 1 kibibyte (KiB) = 1024 bytes. This converter shows both at once so you never have to guess which a given tool means.

    Why your hard drive looks smaller than advertised

    Storage manufacturers advertise capacity in decimal units (a "1 TB" drive is 1,000,000,000,000 bytes), but many operating systems report size in binary units while still labelling them "GB". So that 1 TB drive shows as roughly 931 GiB, even though no space is missing. The bytes are all there; the two systems just count them differently. The gap grows with size, which is why it is most noticeable on large drives.

    Bits vs. bytes

    A bit is a single binary digit (0 or 1); a byte is 8 bits. The distinction matters most for internet speeds, which are quoted in bits per second (Mbps), while file sizes are in bytes (MB). Because there are 8 bits in a byte, a 100 Mbps connection transfers at most about 12.5 megabytes per second, so a 1 GB file takes roughly 80 seconds at full speed, not 10.

    Common reference points

    • 1 byte = 8 bits
    • 1 KB = 1000 bytes; 1 KiB = 1024 bytes
    • 1 GB = 1000 MB (decimal); 1 GiB = 1024 MiB (binary)
    • 1 TB = 1000 GB; 1 TiB = 1024 GiB

    Last updated: July 2026

    Frequently Asked Questions

    What is the difference between KB and KiB?
    KB (kilobyte) traditionally means 1,000 bytes in the SI decimal system, while KiB (kibibyte) explicitly means 1,024 bytes in the binary system. Storage manufacturers use KB/decimal; operating systems often display KiB/binary, causing the common discrepancy in reported drive sizes.
    Why does my hard drive show less storage than advertised?
    Manufacturers advertise storage using decimal units (1TB = 1,000,000,000,000 bytes), but your operating system often displays the same storage using binary units (1024-based), which results in a smaller-looking number like 931GB for a "1TB" drive. No storage is actually missing.
    How many bytes are in a gigabyte?
    In decimal (SI) units, 1 GB = 1,000,000,000 bytes. In binary (IEC) units, 1 GiB = 1,073,741,824 bytes. Most consumer storage marketing uses the decimal definition.
    How long does it take to download 1GB at 100 Mbps?
    At a theoretical maximum of 100 megabits per second, downloading 1 gigabyte (8 gigabits) takes approximately 80 seconds. Real-world speeds are typically lower due to network overhead, so actual times are often longer.
    What is the difference between a bit and a byte?
    A bit is the smallest unit of data, representing a single 0 or 1. A byte consists of 8 bits and is the standard unit for measuring file sizes, memory, and storage capacity.