Compare binary (1024-based) and decimal (1000-based) storage units at every tier from KB to PB. See the exact difference instantly.
Binary and decimal storage units look similar but represent different quantities. A gigabyte (GB) in the decimal system is exactly 1,000,000,000 bytes, while a gibibyte (GiB) in the binary system is 1,073,741,824 bytes—a 7.4% difference. This gap grows at every tier, reaching over 12% at the petabyte scale. The confusion costs consumers real money when purchasing storage and causes capacity planning errors in data centers.
This calculator shows the exact difference between binary (IEC) and decimal (SI) units side by side at every tier. Enter a capacity in either system and see how it translates, including the absolute byte difference and percentage gap. Understanding these differences is crucial for IT professionals, system administrators, and anyone purchasing storage.
Tracking this metric consistently enables technology teams to identify system performance trends and address potential issues before they impact end users or business operations. This measurement provides a critical foundation for capacity planning and performance budgeting, helping teams align infrastructure resources with application requirements and growth projections.
Storage pricing, operating system reporting, and drive labels all use different measurement standards. This calculator reveals the exact byte-level difference at each tier so you can make accurate comparisons, avoid overpaying for storage, and correctly estimate capacity needs. This quantitative approach replaces reactive troubleshooting with proactive monitoring, enabling engineering teams to maintain service level objectives and minimize unplanned system downtime.
Binary value = value × 1024^tier. Decimal value = value × 1000^tier. Difference = Binary − Decimal. Gap% = (Difference / Binary) × 100.
Result: 99.95 GB difference (9.95%)
1 TiB = 1,099,511,627,776 bytes. 1 TB = 1,000,000,000,000 bytes. The difference is 99,511,627,776 bytes, which is approximately 99.95 GB or 93.13 GiB—nearly 10% of the total capacity.
At the kilobyte level, binaary and decimal differ by just 24 bytes per KB (2.4%). But this compounds: at the megabyte level it's 48,576 bytes (4.9%). At the gigabyte level, the gap is 73,741,824 bytes (7.4%). By the terabyte level, the binary value exceeds the decimal by about 99.5 billion bytes (10%).
When you buy a "4 TB" external drive, the manufacturer measured 4,000,000,000,000 bytes. But Windows shows 3.63 TiB (3,725 GiB). That's 275 GiB of "missing" space that was never missing at all. For a 12-disk NAS with 18 TB drives, the total "missing" space is over 9 TiB.
Always standardize on one system for capacity planning. If your monitoring tools report in GiB, budget in GiB. Convert procurement specs from vendor decimal values to binary before adding to capacity plans. This prevents the common mistake of under-provisioning by 7-10%.
Computer scientists originally reused metric prefixes (kilo, mega, giga) for powers of 1024 because they were close to powers of 1000. In 1998, the IEC introduced new prefixes (kibi, mebi, gibi) to eliminate ambiguity, but adoption has been slow.
Hard drive and SSD manufacturers use the decimal (base-1000) system. A "2 TB" drive contains exactly 2,000,000,000,000 bytes. This is technically correct per SI standards but appears as roughly 1.82 TiB in most operating systems.
Windows and most Linux distributions display file sizes in binary units (powers of 1024) but label them with decimal prefixes (GB instead of GiB). macOS switched to decimal units in 2009. This inconsistency is a major source of confusion.
For individual small files, the difference is negligible. A 500 KB file differs by only about 12 KB between systems. But for large datasets, RAID arrays, or cloud storage bills measured in TB, the cumulative difference can represent hundreds of GB and significant cost.
AWS bills in GB where 1 GB = 2^30 bytes (technically GiB). Azure and GCP use similar binary-based billing. Always check the provider's documentation—marketing pages may say "GB" while billing uses binary GiB.
The IEC standard has been available since 1998, and adoption is increasing. Many open-source tools and some Linux distros now use KiB/MiB/GiB correctly. Full adoption is unlikely soon due to marketing preferences and user familiarity.