Data Size & Digital Storage Converter
Convert digital storage units — bits, bytes, kilobytes, megabytes, gigabytes, and terabytes — using both decimal (SI) and binary (IEC) standards, with transfer-time estimates.
Data Size Converter — interactive calculator, computed instantly in your browser.
Digital Storage Units: Bytes, Kilobytes, and the SI vs IEC Split
Decimal (SI) vs Binary (IEC) Scaling
Key Takeaway: Marketing counts in powers of 1,000, operating systems in powers of 1,024 — the 6.9% gap explains every "missing" gigabyte.
Every file size, storage spec, and download estimate passes through the same ladder of digital units — bits, bytes, and their kilo-, mega-, giga-, and tera- multiples. Two standards govern that ladder, and confusing them is the single most common source of "my drive is smaller than advertised" complaints.
1. The Unit Ladder
- Each step multiplies the previous one — MB = 1,000² B, GB = 1,000³ B, TB = 1,000⁴ B in decimal notation
- Binary units use 1,024 per step: 1 MiB = 1,048,576 bytes exactly
- Conversion between systems: value ÷ 1.074 at each step (1 GB = 0.931 GiB)
- Bits measure wire speed (Mbps), bytes measure storage (MB) — divide by 8 to cross over
2. Why Drives Show Fewer Gigabytes
Drive manufacturers count in decimal SI units (1 TB = 1,000,000,000,000 bytes), which is correct under the standard — but Windows and macOS then group those same bytes in binary chunks of 1,024³, reporting 1,000,000,000,000 ÷ 1,073,741,824 ≈ 931 GiB. Nothing is missing; the OS is simply applying a different base. The IEC introduced KiB/MiB/GiB notation in 1998 precisely to end this ambiguity, though marketing never adopted it.
3. Transfer Time: Bridging Size and Speed
- Convert speed to bits per second: 100 Mbps = 100,000,000 bit/s
- Multiply size by 8 to get bits: 1 GB = 8,000,000,000 bit (SI)
- Divide: 8 × 10⁹ ÷ 10⁸ = 80 seconds to download 1 GB at 100 Mbps
- Real throughput runs 80–95% of advertised (protocol overhead), so expect ~95–120 s in practice
🔗 Digital Measurement Cross-References
Storage marketing uses decimal units (1 GB = 1,000,000,000 bytes) while operating systems count binary (1 GiB = 1,073,741,824 bytes) — that gap is why a 1 TB drive shows as ~931 GiB. Explore our 🔄 Unit Conversions Hub for the full dimensional matrix.
Once the size is known, pair it with connection speed to estimate download time, or check live throughput with the network tools below.
Frequently Asked Questions (Data Size Converter)
KB (kilobyte) is decimal: exactly 1,000 bytes. KiB (kibibyte) is binary: exactly 1,024 bytes. Storage makers sell in KB/MB/GB (powers of 1,000); operating systems historically report in binary powers — the IEC suffixes remove the ambiguity.
The drive stores 1,000,000,000,000 bytes (decimal TB), but Windows divides by 1,024³ = 1,073,741,824, giving ≈ 931 GiB. About 7% is the base conversion, not missing capacity.
Decimal (SI): 1 GB = 1,000 MB. Binary (IEC): 1 GiB = 1,024 MiB. Since both standards are in circulation, always state which one you mean when precision matters — file copy speeds and disk tools usually label their base.
Internet speeds use bits (Mbps = megabits per second), while file sizes use bytes. Divide the speed by 8 for byte throughput: a 100 Mbps line transfers 12.5 MB/s, which is why a 120 MB file takes ~10 seconds.
Theoretical: 8,000,000,000 bits ÷ 100,000,000 bit/s = 80 seconds. With protocol overhead expect 95–120 seconds — about 12.5 MB/s sustained.