💾 What is File Size Calculator?
File Size Calculator converts between B, KB, MB, GB, TB, and PB units and estimates download times for various internet speeds. It uses binary units (1024-based) as used by operating systems for accurate conversions. Essential for planning large file transfers, storage capacity, and cloud storage management. Supports speeds from standard internet to gigabit and USB transfer rates.
📊 File Size Unit Reference
| Unit | Size (Binary) | Example |
|---|---|---|
| KB | 1,024 B | Small text document |
| MB | 1,024 KB | High-res photo, MP3 |
| GB | 1,024 MB | Movie, game install |
| TB | 1,024 GB | External drive, backup |
| PB | 1,024 TB | Data center, cloud |
💡 File Size Tips
- Binary vs Decimal: 1TB drive shows ~931GB in Windows (1024 vs 1000 base)
- Mbps vs MB/s: 100Mbps = 12.5MB/s (8 bits = 1 byte)
- Real speed: Actual download is typically 70-80% of rated speed
- 5G note: Theoretical 10Gbps, real-world average 100-200Mbps
Frequently Asked Questions
Why does my 1TB drive show only 931GB in Windows?▼
Manufacturers use 1TB = 1,000GB (decimal), but operating systems use 1TB = 1,024GB (binary). So 1,000,000,000,000 bytes ÷ 1,099,511,627,776 ≈ 931GB.
Why is my download slower than my internet speed?▼
Internet speed is measured in Mbps (bits), downloads show MB/s (bytes). Since 8 bits = 1 byte, 100Mbps internet means max 12.5MB/s download speed.
Why is USB 3.0 slower than expected?▼
USB 3.0's 5Gbps is the theoretical maximum. Real-world speeds depend on controller, drive speed, and file count—typically achieving 200-400MB/s.